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  • Create DFS replica from a NAS drive

    - by Mark
    We have two offices, at two different locations. In one we have a NAS, with some shares. We also have a Domain Controller using Windows 2003 R2. We have setup a second Domain Controller using Windows 2003 R2 to put that in the second office. What we would also like is to replicate the NAS drive onto the second Domain Controller so in the second office they have a local copy, and that their changes are replicated back to the NAS. Is there a way to setup DFS replication to do this? Or will it only work with local folders on each Server? Update 1 Sept Base on the answer below, I think I need to add some clarification. The real issue is that the NAS which hosts the shared folder that we want to replicate is external to both servers. And we have a particular share mapped to say S: . In the replication setup it doesnt seem to accept network shares external to the server to be candidates for replication. I can understand why, I just need confirmation that DFSR will only work with block devices that are local on at least one server. Is this the case?

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  • What are the best linux permissions to use for my website?

    - by Nic
    This is a Canonical Question about File Permissions on a Linux web server. I have a Linux web server running Apache2 that hosts several websites. Each website has its own folder in /var/www/. /var/www/contoso.com/ /var/www/contoso.net/ /var/www/fabrikam.com/ The base directory /var/www/ is owned by root:root. Apache is running as www-data:www-data. The Fabrikam website is maintained by two developers, Alice and Bob. Both Contoso websites are maintained by one developer, Eve. All websites allow users to upload images. If a website is compromised, the impact should be as limited as possible. I want to know the best way to set up permissions so that Apache can serve the content, the website is secure from attacks, and the developers can still make changes. One of the websites is structured like this: /var/www/fabrikam.com /cache /modules /styles /uploads /index.php How should the permissions be set on these directories and files? I read somewhere that you should never use 777 permissions on a website, but I don't understand what problems that could cause. During busy periods, the website automatically caches some pages and stores the results in the cache folder. All of the content submitted by website visitors is saved to the uploads folder.

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  • Sizing Switches for Storage and Production

    - by Untalented
    Couple questions. Should you always completely separate the storage network switches from production switches or are VLANs fine to segment this traffic? Is there a golden rule here? How do you properly size a switch for your environment based on the specifications the manufacturer provide (Throughput, Forwarding Throughput, Stacking Throughput, Max Mac)? If you have two switch options and one has a maximum Mac address of 8,000 vs. another with 16,0000. What does this really mean to me? How do make sure one vs. another is sized properly for me? Besides VLAN and Jumbo Frame support, is there any other "Must" haves for a virtual environments production or storage networks? There is a wealth of knowledge on sizing SANs and such, but this seems equally important and it's quite challenging to find as much information. -- Just to add some tidbits of information for the environment. This setup above is referring to the data centers which supports two different locations which have about 100 users between the two in total. The storage traffic will be iSCSI and will be 3 ESXi Hosts and one SAN housing about 2.7TB of data. Since there is currently no storage network in place (no SAN), I'm having a hard time regarding #2 to really determine what backplane throughput and switch specifications will be sufficient.

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  • Google Apps routing to different servers, depending on domain

    - by Philip
    We are investigating Google Apps for Education for our group of schools. Currently, each school uses their own Exchange (2003) server. Each school has its own domain which I have added to Google Apps as additional domains. I would like to start transitioning certain staff and some new pupils over to Google Apps to start testing. In this interim phase, I need mail to be routed through Google Apps and then, if no appropriate mail box is found, route on to the individual schools depending on the recipient. I do know that it is possible to route mail that does not have an appropriate Google Apps mail account to a single server - under "Settings / E-mail Settings / General Settings / Routing / E-mail routing". This works well for a single organisation where all the extra mail is destined for one place. I do know that it is possible to set up Routes, under "Settings / E-mail Settings / Hosts" and then use rules, found under "Settigns / E-mail Settings / General Settings / Routing / Receiving Routing". I can then filter based on e-mail domain and forward on to the necessary server. My problem with this, as I understand it, is that it ignores the users that have Google Apps accounts set up and sends all mail to the Exchange server. Are there any solutions for this predicament? Many thanks!

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  • What is the alternative of Apache's global Alias in IIS? (e.g. Alias /phpMyAdmin "c:/AppServ/www/phpMyAdmin")

    - by Sk8erPeter
    I know there's an "Add Virtual Directory..." option in every given sites in IIS with which I can set up e.g. phpMyAdmin's path to be reached with prepending /phpmyadmin to the address (e.g. http://example.com/phpmyadmin), but isn't there a "global" setting similar to Apache's Alias? For example, in Apache this setting looks like this: <IfModule mod_alias.c> Alias /phpMyAdmin "c:/AppServ/www/phpMyAdmin" Alias /phpmyadmin "c:/AppServ/www/phpMyAdmin" </IfModule> This way I reach phpmyadmin with every hosts. (http://example1.com/phpmyadmin, http://example2.com/phpmyadmin also does work) But in IIS, do I have to add a virtual directory to every sites? I'm just curious, because we would like to serve some domain's content, so there would be multiple sites. It would be more comfortable to do it once (or have the opportunity to remove it once), but if I have to, I do add a virtual directory for each sites. (I know, maybe it's the better solution, because I can have a site where I don't want phpmyadmin to be available, but I was just curious.) Thanks in advance!

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  • Apache not routing to tomcat on correct Virtual host

    - by ttheobald
    We are looking at moving from Websphere to Tomcat. I'm trying to send traffic to tomcat from apache web server based on the virtual host directives in apache web server. After some playing around I have it sort of working, but I'm noticing that if I have a JKMount directive in the first VirtualHost in apache, all virtualHosts will send to the application server. If I have the JKMount in Virtual hosts further down in the configs, then only that VirtualHost works with the request. For Example, with the configs below here are my symptoms mysite.com/Webapp1/ -- I resolve to the proper application mysite2.com/Webapp1/ -- I resolve to the proper application (bad!) mysite.com/MonitorApp/ -- I resolve to the proper application mysite2.com/MonitorApp/ -- I resolve to the proper application (bad!) mysite.com/Webapp2/ -- I DO NOT get to the app (good) mysite2.com/Webapp2/ -- I resolve to the proper application Here's what my web server virtualhosts look like. <VirtualHost 255.255.255.1:80> ServerName mysite.com ServerAlias aliasmysite.ca ##all our rewrite rules JkMount /Webapp1/* LoadBalanceWorker JKmount /MonitorApp/* LoadBalanceWorker </VirtualHost> <VirtualHost 255.255.255.2:80> ServerName mysite2.com ServerAlias aliasmysite2.ca ##all our rewrite rules JkMount /Webapp2/* LoadBalanceWorker </VirtualHost> we are running apache webserver 2.2.10 and tomcat 7.0.29 on Solaris10 I've posted an image of our architecture here. http://imgur.com/IFaA6Rh I HAVE not defined VirtualHosts on Tomcat. Based on what I've read, my understanding is that it's only needed if I'm accessing Tomcat directly. Any assistance is appreciated. Edit Here's my worker.properties. worker.list= LoadBalanceWorker,App1,App2 worker.intApp1.port=8009 worker.intApp1.host=10.15.8.8 worker.intApp1.type=ajp13 worker.intApp1.lbfactor=1 worker.intApp1.socket_timeout=30 worker.intApp1.socket_connect_timeout=5000 worker.intApp1.fail_on_status=302,500,503 worker.intApp1.recover_time=30 worker.intApp2.port=8009 worker.intApp2.host=10.15.8.9 worker.intApp2.type=ajp13 worker.intApp2.lbfactor=1 worker.intApp2.socket_timeout=30 worker.intApp2.socket_connect_timeout=5000 worker.intApp2.fail_on_status=302,500,503 worker.intApp2.recover_time=30 worker.LoadBalanceWorker.type=lb worker.LoadBalanceWorker.balanced_workers=intApp1,intApp2 worker.LoadBalanceWorker.sticky_session=1

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  • DNS/Nameserver issue. Can't ping IP or domain

    - by Tar
    I get this when I ping an IP: 21:31:50.136623 IP SITE_IP > 173.194.33.4: ICMP echo request, id 14941, seq 1, length 64 21:31:51.136138 IP SITE_IP > 173.194.33.4: ICMP echo request, id 14941, seq 2, length 64 21:31:52.136118 IP SITE_IP > 173.194.33.4: ICMP echo request, id 14941, seq 3, length 64 21:31:53.136129 IP SITE_IP > 173.194.33.4: ICMP echo request, id 14941, seq 4, length 64 21:31:54.136102 IP SITE_IP > 173.194.33.4: ICMP echo request, id 14941, seq 5, length 64 21:31:55.136153 IP SITE_IP > 173.194.33.4: ICMP echo request, id 14941, seq 6, length 64 and when I ping a domain: 21:29:33.631583 IP 74.125.189.19.52085 > SITE_IP.domain: 28952 A? google.com.MY_DOMAIN. (42) 21:29:38.626553 IP SITE_IP.42280 > 8.8.4.4.domain: 52435+ A? google.com.MY_DOMAIN. (42) 21:29:38.652675 IP 74.125.189.22.63658 > SITE_IP.domain: 36178 A? google.com.MY_DOMAIN. (42) 21:29:43.631626 IP SITE_IP.48205 > 8.8.8.8.domain: 52435+ A? google.com.MY_DOMAIN. (42) The pinging of a domain is what worries me, because it looks like it is checking my DNS files for the resolution. Here is etc/resolv.conf nameserver 8.8.8.8 nameserver 8.8.4.4 /etc/hosts 127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4 ::1 localhost localhost.localdomain localhost6 localhost6.localdomain6 SITE_iP server.MY_DOMAIN.com server Will also add that I am seeing a number of 'SERVFAIL'.. I have no idea what could be causing this problem. If there is any other information I need to provide, let me know. I'm using CentOS.

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  • Can I host multiple sites with one Amazon EC2 instance [duplicate]

    - by user22
    This question already has an answer here: Can you help me with my capacity planning? 2 answers I currently have VPS server and I pay around $75 per month and I get: 40GB HD 2Gb RAM 100GB BW 6 core cpu (but i dont use much) I have only one live website running and traffic is only max 100 user visit per day. I mostly do the my testing stuff and some of my inter sites for playing with coding. But I do need one server. I am thinking of moving to Amazon EC2 if the price diff is not so much because then I can learn some more stuff. I am thinking of getting the 3 years Heavy utilization Reserved instance because my server will be running all day and night. I tried their online caluclator with Medium Instance Heavy reserved for 3 years for EC2 it comes $31 per month(effective price) and for EBS and S3 , I think even if thats it $40 for all other stuff. I will be at no loss for what I am getting at present. Am i correct or I missed something?? Now In my current VPS I have Apache for PHP sites and MOD wsgi for python sites. I am not sure if I will be able to do all that stuff in Amazon EC2. Can I host python and PHP sites both in Amazon EC2 instance using Named Virtual Hosts and Ngnix

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  • very slow connection to ssh server from client (but not other servers)

    - by AntonOfTheWoods
    I have an Ubuntu 12.04 laptop that is taking so long to connect to various servers (in different data centres) that it seems like a bit of a lottery whether I'll actually get a connection. If I connect to the servers between themselves it's instantaneous, and I've set UseDNS no AddressFamily inet On the servers I'm connecting to (and rebooted for good measure). I also put in the reverse DNS+IP of the cable connection I'm connecting from. If I connect from the laptop via telnet: telnet my.server 22 Then the connection is also instantaneous, so it doesn't appear to be a problem with an intervening firewall. I have the same behaviour whether I connect with the IP, a short name in my hosts or the FQDN. I'm connecting with a 50mbps (cable, sync) connection so that doesn't appear to be the problem, and when I do finally get a connection then it's a good, quick, stable one. I have tried listening on another port (8000) and that makes no difference. Web and other connections from the laptop to the machine are also very good. Does anyone have any ideas here?

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  • Apache Cache with multiple CacheRoots

    - by Tobias Greitzke
    I configured Apache with a CacheRoot directory for each of my domains / virtual hosts: <VirtualHost> ServerName domain1.tld ... CacheRoot /var/www/vhosts/domain1.tld/httpdocs/cache ... </VirtualHost> <VirtualHost> ServerName domain2.tld ... CacheRoot /var/www/vhosts/domain2.tld/httpdocs/cache ... </VirtualHost> I have this up and running for quite a while and so fare it's working pretty well except that I have to empty out the cache manually every so often because htcacheclean does't know of the different directories. Now I would like to setup htcacheclean to watch over the cache directories but as fare as I understand the manual, I can only set it to one cache directory. I would like to do something like this but that doesn't work: <VirtualHost> ServerName domain1.tld ... CacheRoot /var/www/vhosts/domain1.tld/httpdocs/cache htcacheclean -n -t -p/var/www/vhosts/domain1.tld/httpdocs/cache -l1024M ... </VirtualHost> Is it even right to have multiple cache directorys or should I work with just one cache directory for all of the domains?

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  • How to setup a virtual host in Ubuntu running on Amazon EC2 instance?

    - by Rade
    I have an app that's accessible via 1.2.3.4/myapp. The app is installed in /var/www/myapp. I've set up a subdomain(apps.mydomain.com) that points to 1.2.3.4. I want the server to point to var/www/myapp if I type apps.mydomain.com/myapp, how do I do that? I have experience creating virtual hosts(lots of them) locally but I'm lost because it's now in production and it's a little different. Here's my virtual host config: <VirtualHost *:80> ServerAdmin webmaster@localhost ServerName apps.mydomain.com/myapp DocumentRoot /var/www/myapp/public <Directory /> Options FollowSymLinks AllowOverride All </Directory> <Directory /var/www/> Options Indexes FollowSymLinks MultiViews AllowOverride All Order allow,deny allow from all </Directory> ScriptAlias /cgi-bin/ /usr/lib/cgi-bin/ <Directory "/usr/lib/cgi-bin"> AllowOverride All Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch Order allow,deny Allow from all </Directory> ErrorLog ${APACHE_LOG_DIR}/error.log # Possible values include: debug, info, notice, warn, error, crit, # alert, emerg. LogLevel warn CustomLog ${APACHE_LOG_DIR}/access.log combined </VirtualHost> Any idea why I still see the files instead of pointing me to the document root? Just in case someone might ask, the app is based on Laravel 4 framework. It's really bad right now because anyone can access the files from the browser.

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  • Automatic switching of network card when vm is moved

    - by spock
    I have two hosts in a pool and I used to be able to move the vm around and they will start without any problem. But after I played around with some network setting, which I don't remember what, I started getting "This VM needs storage that cannot be seen from that server" message. As you can tell I am a beginner with Xenserver. Here is the very simple environment: 2 host servers with their own local hard disk and network card. One is a Pool master. Problem: Power off a vm and move vm from one server to another, or clone one vm to the other server. It used to be able to start up right away. Now, I need to delete one of the network that does not belong to the server, then it will start. Otherwise, the above error msg popup. The two networks (one for each network card in each host) are in the Networking tab of the vm, as well as in the host's networking tab. I googled but all I got to empty the DVD drive, which is not the problem here. Thanks in advance!

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  • How can I assign DHCP leases from a script?

    - by devicenull
    I have an environment where there is one DHCP server servicing a number of different hosts/vlans. The switches are configured to forward the DHCP requests over (via ip-helper) and include information about the port (option 82). I'd like to take that information and translate it into an actual lease for the server. I don't think it's particularly feasible for me to pregenerate a list of available leases, but I should be able to determine an address for a lease as it comes in. Is there an DHCP server that can execute a script when it receives a request? (Note: I'm looking to assign the IP from the script, not have the DHCP server assign an IP then execute the script) Edit: So, ultimately I'm trying to provide DHCP/PXE services over a large number of distinct vlans. This is so we can do OS installs via PXE booting without having to have a separate PXE vlan. I've got the switch config down no problem, and I have the DHCP server recognizing option 82. I need a way to pull DHCP assignments from another system (this other system would know what subnet to use on what vlan), but I do not want to have to pregenerate a list of vlan:DHCP range pairs.

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  • Mail server DNS failed to resolved by Mac clients

    - by Concordus Applications
    We have two internal DNS servers. One is located on a linux server box and the other is the router's DNS management. We set the linux box as primary DNS via DHCP and the router as secondary. We have a few Mac clients that are accessing our internal mail server (hostnamed "mail" internally). When using IMAP or SMTP against the mail server internally, the mac boxes will sometimes fail to locate the server. If I use NSLOOKUP I can see that "mail" is pointed to the correct IP address and is being resolved via the correct DNS server, but if I ping "mail" it fails. ~ (bash)$ nslookup mail Server: 254.254.254.206 Address: 254.254.254.206#53 Name: mail.example.com Address: 254.254.254.205 Note: I replaced our actual internal IP address with 254.254.254.* If I wait a few minutes (3-5 minutes), somehow it resolves itself and sends successfully. This happens multiple times a day. The /etc/hosts file on the mac boxes is the default config. ## # Host Database # # localhost is used to configure the loopback interface # when the system is booting. Do not change this entry. ## 127.0.0.1 localhost 255.255.255.255 broadcasthost ::1 localhost fe80::1%lo0 localhost Is there something about Mac clients I should know to prevent this failed DNS resolution? Client boxes are: OSX 10.7.4, 8GB RAM, i5 MacBooks Server is: Ubuntu 12.04 Server

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  • Virtual hosting in lighttpd?

    - by lighttpdnewbie
    Ok, here it goes... I've seen some other posts dealing with this, but it didn't help that much. I am using windows XP. My problem is with trying to get lighttpd working with virtual hosts. Now, I managed to get everything up and working with the default /htdocs and the default page shows up just fine on the internet, but since I have several sites to host, I need virtual hosting. I managed to do it in apache, so I guessed it would work out just fine in lighttpd, but apparently I'm missing something. Ok, let's say I have domain (www.)example.org. I want everyone using that url going to the correct index.html, obviously. Let's say that index.html is in directory "websites/website1" placed under the lighttpd dir. (thus, the full path is c:/ProgramsFiles/lighttpd/websites/website1/index.html) Now: how, exactly, do I set up my virtual host (in the config file)? In detail, please, since I've tried for hours with the vague hints I got from fora and such, but it doesn't work. Also; is there something additional to do? Change the "server.bind" or get rid of the default server.document-root, or something? I appreciate all the help you can give! Especially if it's a verbatim/step-by-step solution you're offering! ;-p Edit: And, yes, my mod_simple_vhost has been enabled.

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  • My server is taking too long to respond when I connect to it outside the local network [closed]

    - by Buzu
    I have my local server online most of the time because it is easy for clients to access a url and see how their project is coming along. They can see updates in real time. However, I got a message from one of my clients saying that the server was not responding. I have a hosts file, and in that file I have my server's address pointed to the local ip. This is because some problem with the ftp. Due to this setup, I had not noticed that the server was not accessible from outside the local network. The address is http://imbuzu.dyndns.info SSH works fine, I can connect from my windows machine to the server, but HTTP does not. The server is taking too long to respond. Looking at the logs, I see that the last incoming connection to the server from outside the network is this: 77.242.153.180 - - [04/Dec/2012:12:11:01 -0800] "\xce\x89\x8d\x85b\ro" 400 317 "-" "-" I'm going to restart the server, but I doubt that will have any effect on it. --EDIT-- I restarted the server, and it did not help. Also, I pinged the server and it seems to be resolving correctly.

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  • Can't connect to FTP server from a specific location

    - by wv_pip
    Last week while uploading website files to our server via FTP, the transfer failed. Ever since then, I haven't been able to connect to the server from work. I can connect just fine from home, or by using an FTP app on my cell phone as long as I'm on the cell network. I can't access the server from any machine on my work network. It's not a credential issue, either. The error message that I always get says that a connection cannot be established, and I am never prompted for my credentials. I have changed absolutely nothing on our domain controller or our firewall/router. I've contacted our ISP (who hosts the website/FTP server) and they can't find anything wrong on their end. They insist that it must be something here at the office that is blocking access. I've also tested access to other FTP servers (ea.com, nvidia.com, etc.) so I know that port 21 is not being blocked. I'm totally stumped. Any help is much appreciated. EDIT: wireshark info here: http://www.cloudshark.org/captures/85a118ae9296?filter=ip.dst%3D%3D66.118.64.208

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  • Access denied when trying to open files/folders after reinstall [closed]

    - by user711532
    Possible Duplicate: Access Denied when saving a file in Windows 7 I installed Windows 7 fresh on a new machine. Now when I unarchive (winrar or 7z etc. ) to Program files (x86) (for example), access denied. Even if I copy a file to a folder I installed an app to it is still access denied. I checked the security, it looks like full control is given to the creator - this is weird as I never ran across this before (same version of Windows 7 - its just a fresh install after some new hardware). It is the same effect as if I was editing the hosts file, and you do not use "run as admin" you will not be able to save it, yo will have to save it somewhere else. This "file copy" issue I ran into is the same. I could change all these permissions, however this is something I never had to do before. I am the admin, why did the install, not give me "full control"? How can this be globally fixed. I cannot change the permissions - they are greyed out - so that is weird as well. If I was a standard reason, It would make sense, however, again, I am the admin.

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  • Domain name is bringing up wrong site

    - by daniel0mullins
    I have a VPS that hosts several domains. I have set up Apache in the following manner: First VirtualHost /etc/apache2/sites-available/somedomain.com <VirtualHost somedomain.com:80> ServerName somedomain.com ServerAlias www.somedomain.com ... </VirtualHost> Second VirtualHost /etc/apache2/sites-available/someotherdomain.com <VirtualHost someotherdomain.com:80> ServerName someotherdomain.com ServerAlias www.someotherdomain.com ... </VirtualHost> Then I symlink the config files from sites-available to sites-enabled and all is well. I had a need to 'turn off' someotherdomain.com, so I removed the symlink to /etc/apache2/sites-available/someotherdomain.com from sites-enabled and the site no longer shows up... BUT typing someotherdomain.com into a web browser brings up somedomain.com!!! I need it to not resolve at all. Does somethiing need to be done in the VirtualHost to just automatically return a 500 or something along those lines. I really don't want people to reach one website from a different domain. Thanks! EDIT ports.conf looks like this NameVirtualHost *:80 Listen 80 <IfModule mod_ssl.c> NameVirtualHost *:443 Listen 443 </IfModule> <IfModule mod_gnutls.c> Listen 443 </IfModule>

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  • Diving into OpenStack Network Architecture - Part 2 - Basic Use Cases

    - by Ronen Kofman
      rkofman Normal rkofman 4 138 2014-06-05T03:38:00Z 2014-06-05T05:04:00Z 3 2735 15596 Oracle Corporation 129 36 18295 12.00 Clean Clean false false false false EN-US X-NONE HE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:Arial; mso-bidi-theme-font:minor-bidi; mso-bidi-language:AR-SA;} In the previous post we reviewed several network components including Open vSwitch, Network Namespaces, Linux Bridges and veth pairs. In this post we will take three simple use cases and see how those basic components come together to create a complete SDN solution in OpenStack. With those three use cases we will review almost the entire network setup and see how all the pieces work together. The use cases we will use are: 1.       Create network – what happens when we create network and how can we create multiple isolated networks 2.       Launch a VM – once we have networks we can launch VMs and connect them to networks. 3.       DHCP request from a VM – OpenStack can automatically assign IP addresses to VMs. This is done through local DHCP service controlled by OpenStack Neutron. We will see how this service runs and how does a DHCP request and response look like. In this post we will show connectivity, we will see how packets get from point A to point B. We first focus on how a configured deployment looks like and only later we will discuss how and when the configuration is created. Personally I found it very valuable to see the actual interfaces and how they connect to each other through examples and hands on experiments. After the end game is clear and we know how the connectivity works, in a later post, we will take a step back and explain how Neutron configures the components to be able to provide such connectivity.  We are going to get pretty technical shortly and I recommend trying these examples on your own deployment or using the Oracle OpenStack Tech Preview. Understanding these three use cases thoroughly and how to look at them will be very helpful when trying to debug a deployment in case something does not work. Use case #1: Create Network Create network is a simple operation it can be performed from the GUI or command line. When we create a network in OpenStack the network is only available to the tenant who created it or it could be defined as “shared” and then it can be used by all tenants. A network can have multiple subnets but for this demonstration purpose and for simplicity we will assume that each network has exactly one subnet. Creating a network from the command line will look like this: # neutron net-create net1 Created a new network: +---------------------------+--------------------------------------+ | Field                     | Value                                | +---------------------------+--------------------------------------+ | admin_state_up            | True                                 | | id                        | 5f833617-6179-4797-b7c0-7d420d84040c | | name                      | net1                                 | | provider:network_type     | vlan                                 | | provider:physical_network | default                              | | provider:segmentation_id  | 1000                                 | | shared                    | False                                | | status                    | ACTIVE                               | | subnets                   |                                      | | tenant_id                 | 9796e5145ee546508939cd49ad59d51f     | +---------------------------+--------------------------------------+ Creating a subnet for this network will look like this: # neutron subnet-create net1 10.10.10.0/24 Created a new subnet: +------------------+------------------------------------------------+ | Field            | Value                                          | +------------------+------------------------------------------------+ | allocation_pools | {"start": "10.10.10.2", "end": "10.10.10.254"} | | cidr             | 10.10.10.0/24                                  | | dns_nameservers  |                                                | | enable_dhcp      | True                                           | | gateway_ip       | 10.10.10.1                                     | | host_routes      |                                                | | id               | 2d7a0a58-0674-439a-ad23-d6471aaae9bc           | | ip_version       | 4                                              | | name             |                                                | | network_id       | 5f833617-6179-4797-b7c0-7d420d84040c           | | tenant_id        | 9796e5145ee546508939cd49ad59d51f               | +------------------+------------------------------------------------+ We now have a network and a subnet, on the network topology view this looks like this: Now let’s dive in and see what happened under the hood. Looking at the control node we will discover that a new namespace was created: # ip netns list qdhcp-5f833617-6179-4797-b7c0-7d420d84040c   The name of the namespace is qdhcp-<network id> (see above), let’s look into the namespace and see what’s in it: # ip netns exec qdhcp-5f833617-6179-4797-b7c0-7d420d84040c ip addr 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN     link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00     inet 127.0.0.1/8 scope host lo     inet6 ::1/128 scope host        valid_lft forever preferred_lft forever 12: tap26c9b807-7c: <BROADCAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN     link/ether fa:16:3e:1d:5c:81 brd ff:ff:ff:ff:ff:ff     inet 10.10.10.3/24 brd 10.10.10.255 scope global tap26c9b807-7c     inet6 fe80::f816:3eff:fe1d:5c81/64 scope link        valid_lft forever preferred_lft forever   We see two interfaces in the namespace, one is the loopback and the other one is an interface called “tap26c9b807-7c”. This interface has the IP address of 10.10.10.3 and it will also serve dhcp requests in a way we will see later. Let’s trace the connectivity of the “tap26c9b807-7c” interface from the namespace.  First stop is OVS, we see that the interface connects to bridge  “br-int” on OVS: # ovs-vsctl show 8a069c7c-ea05-4375-93e2-b9fc9e4b3ca1     Bridge "br-eth2"         Port "br-eth2"             Interface "br-eth2"                 type: internal         Port "eth2"             Interface "eth2"         Port "phy-br-eth2"             Interface "phy-br-eth2"     Bridge br-ex         Port br-ex             Interface br-ex                 type: internal     Bridge br-int         Port "int-br-eth2"             Interface "int-br-eth2"         Port "tap26c9b807-7c"             tag: 1             Interface "tap26c9b807-7c"                 type: internal         Port br-int             Interface br-int                 type: internal     ovs_version: "1.11.0"   In the picture above we have a veth pair which has two ends called “int-br-eth2” and "phy-br-eth2", this veth pair is used to connect two bridge in OVS "br-eth2" and "br-int". In the previous post we explained how to check the veth connectivity using the ethtool command. It shows that the two are indeed a pair: # ethtool -S int-br-eth2 NIC statistics:      peer_ifindex: 10 . .   #ip link . . 10: phy-br-eth2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 . . Note that “phy-br-eth2” is connected to a bridge called "br-eth2" and one of this bridge's interfaces is the physical link eth2. This means that the network which we have just created has created a namespace which is connected to the physical interface eth2. eth2 is the “VM network” the physical interface where all the virtual machines connect to where all the VMs are connected. About network isolation: OpenStack supports creation of multiple isolated networks and can use several mechanisms to isolate the networks from one another. The isolation mechanism can be VLANs, VxLANs or GRE tunnels, this is configured as part of the initial setup in our deployment we use VLANs. When using VLAN tagging as an isolation mechanism a VLAN tag is allocated by Neutron from a pre-defined VLAN tags pool and assigned to the newly created network. By provisioning VLAN tags to the networks Neutron allows creation of multiple isolated networks on the same physical link.  The big difference between this and other platforms is that the user does not have to deal with allocating and managing VLANs to networks. The VLAN allocation and provisioning is handled by Neutron which keeps track of the VLAN tags, and responsible for allocating and reclaiming VLAN tags. In the example above net1 has the VLAN tag 1000, this means that whenever a VM is created and connected to this network the packets from that VM will have to be tagged with VLAN tag 1000 to go on this particular network. This is true for namespace as well, if we would like to connect a namespace to a particular network we have to make sure that the packets to and from the namespace are correctly tagged when they reach the VM network. In the example above we see that the namespace interface “tap26c9b807-7c” has vlan tag 1 assigned to it, if we examine OVS we see that it has flows which modify VLAN tag 1 to VLAN tag 1000 when a packet goes to the VM network on eth2 and vice versa. We can see this using the dump-flows command on OVS for packets going to the VM network we see the modification done on br-eth2: #  ovs-ofctl dump-flows br-eth2 NXST_FLOW reply (xid=0x4):  cookie=0x0, duration=18669.401s, table=0, n_packets=857, n_bytes=163350, idle_age=25, priority=4,in_port=2,dl_vlan=1 actions=mod_vlan_vid:1000,NORMAL  cookie=0x0, duration=165108.226s, table=0, n_packets=14, n_bytes=1000, idle_age=5343, hard_age=65534, priority=2,in_port=2 actions=drop  cookie=0x0, duration=165109.813s, table=0, n_packets=1671, n_bytes=213304, idle_age=25, hard_age=65534, priority=1 actions=NORMAL   For packets coming from the interface to the namespace we see the following modification: #  ovs-ofctl dump-flows br-int NXST_FLOW reply (xid=0x4):  cookie=0x0, duration=18690.876s, table=0, n_packets=1610, n_bytes=210752, idle_age=1, priority=3,in_port=1,dl_vlan=1000 actions=mod_vlan_vid:1,NORMAL  cookie=0x0, duration=165130.01s, table=0, n_packets=75, n_bytes=3686, idle_age=4212, hard_age=65534, priority=2,in_port=1 actions=drop  cookie=0x0, duration=165131.96s, table=0, n_packets=863, n_bytes=160727, idle_age=1, hard_age=65534, priority=1 actions=NORMAL   To summarize we can see that when a user creates a network Neutron creates a namespace and this namespace is connected through OVS to the “VM network”. OVS also takes care of tagging the packets from the namespace to the VM network with the correct VLAN tag and knows to modify the VLAN for packets coming from VM network to the namespace. Now let’s see what happens when a VM is launched and how it is connected to the “VM network”. Use case #2: Launch a VM Launching a VM can be done from Horizon or from the command line this is how we do it from Horizon: Attach the network: And Launch Once the virtual machine is up and running we can see the associated IP using the nova list command : # nova list +--------------------------------------+--------------+--------+------------+-------------+-----------------+ | ID                                   | Name         | Status | Task State | Power State | Networks        | +--------------------------------------+--------------+--------+------------+-------------+-----------------+ | 3707ac87-4f5d-4349-b7ed-3a673f55e5e1 | Oracle Linux | ACTIVE | None       | Running     | net1=10.10.10.2 | +--------------------------------------+--------------+--------+------------+-------------+-----------------+ The nova list command shows us that the VM is running and that the IP 10.10.10.2 is assigned to this VM. Let’s trace the connectivity from the VM to VM network on eth2 starting with the VM definition file. The configuration files of the VM including the virtual disk(s), in case of ephemeral storage, are stored on the compute node at/var/lib/nova/instances/<instance-id>/. Looking into the VM definition file ,libvirt.xml,  we see that the VM is connected to an interface called “tap53903a95-82” which is connected to a Linux bridge called “qbr53903a95-82”: <interface type="bridge">       <mac address="fa:16:3e:fe:c7:87"/>       <source bridge="qbr53903a95-82"/>       <target dev="tap53903a95-82"/>     </interface>   Looking at the bridge using the brctl show command we see this: # brctl show bridge name     bridge id               STP enabled     interfaces qbr53903a95-82          8000.7e7f3282b836       no              qvb53903a95-82                                                         tap53903a95-82    The bridge has two interfaces, one connected to the VM (“tap53903a95-82 “) and another one ( “qvb53903a95-82”) connected to “br-int” bridge on OVS: # ovs-vsctl show 83c42f80-77e9-46c8-8560-7697d76de51c     Bridge "br-eth2"         Port "br-eth2"             Interface "br-eth2"                 type: internal         Port "eth2"             Interface "eth2"         Port "phy-br-eth2"             Interface "phy-br-eth2"     Bridge br-int         Port br-int             Interface br-int                 type: internal         Port "int-br-eth2"             Interface "int-br-eth2"         Port "qvo53903a95-82"             tag: 3             Interface "qvo53903a95-82"     ovs_version: "1.11.0"   As we showed earlier “br-int” is connected to “br-eth2” on OVS using the veth pair int-br-eth2,phy-br-eth2 and br-eth2 is connected to the physical interface eth2. The whole flow end to end looks like this: VM è tap53903a95-82 (virtual interface)è qbr53903a95-82 (Linux bridge) è qvb53903a95-82 (interface connected from Linux bridge to OVS bridge br-int) è int-br-eth2 (veth one end) è phy-br-eth2 (veth the other end) è eth2 physical interface. The purpose of the Linux Bridge connecting to the VM is to allow security group enforcement with iptables. Security groups are enforced at the edge point which are the interface of the VM, since iptables nnot be applied to OVS bridges we use Linux bridge to apply them. In the future we hope to see this Linux Bridge going away rules.  VLAN tags: As we discussed in the first use case net1 is using VLAN tag 1000, looking at OVS above we see that qvo41f1ebcf-7c is tagged with VLAN tag 3. The modification from VLAN tag 3 to 1000 as we go to the physical network is done by OVS  as part of the packet flow of br-eth2 in the same way we showed before. To summarize, when a VM is launched it is connected to the VM network through a chain of elements as described here. During the packet from VM to the network and back the VLAN tag is modified. Use case #3: Serving a DHCP request coming from the virtual machine In the previous use cases we have shown that both the namespace called dhcp-<some id> and the VM end up connecting to the physical interface eth2  on their respective nodes, both will tag their packets with VLAN tag 1000.We saw that the namespace has an interface with IP of 10.10.10.3. Since the VM and the namespace are connected to each other and have interfaces on the same subnet they can ping each other, in this picture we see a ping from the VM which was assigned 10.10.10.2 to the namespace: The fact that they are connected and can ping each other can become very handy when something doesn’t work right and we need to isolate the problem. In such case knowing that we should be able to ping from the VM to the namespace and back can be used to trace the disconnect using tcpdump or other monitoring tools. To serve DHCP requests coming from VMs on the network Neutron uses a Linux tool called “dnsmasq”,this is a lightweight DNS and DHCP service you can read more about it here. If we look at the dnsmasq on the control node with the ps command we see this: dnsmasq --no-hosts --no-resolv --strict-order --bind-interfaces --interface=tap26c9b807-7c --except-interface=lo --pid-file=/var/lib/neutron/dhcp/5f833617-6179-4797-b7c0-7d420d84040c/pid --dhcp-hostsfile=/var/lib/neutron/dhcp/5f833617-6179-4797-b7c0-7d420d84040c/host --dhcp-optsfile=/var/lib/neutron/dhcp/5f833617-6179-4797-b7c0-7d420d84040c/opts --leasefile-ro --dhcp-range=tag0,10.10.10.0,static,120s --dhcp-lease-max=256 --conf-file= --domain=openstacklocal The service connects to the tap interface in the namespace (“--interface=tap26c9b807-7c”), If we look at the hosts file we see this: # cat  /var/lib/neutron/dhcp/5f833617-6179-4797-b7c0-7d420d84040c/host fa:16:3e:fe:c7:87,host-10-10-10-2.openstacklocal,10.10.10.2   If you look at the console output above you can see the MAC address fa:16:3e:fe:c7:87 which is the VM MAC. This MAC address is mapped to IP 10.10.10.2 and so when a DHCP request comes with this MAC dnsmasq will return the 10.10.10.2.If we look into the namespace at the time we initiate a DHCP request from the VM (this can be done by simply restarting the network service in the VM) we see the following: # ip netns exec qdhcp-5f833617-6179-4797-b7c0-7d420d84040c tcpdump -n 19:27:12.191280 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from fa:16:3e:fe:c7:87, length 310 19:27:12.191666 IP 10.10.10.3.bootps > 10.10.10.2.bootpc: BOOTP/DHCP, Reply, length 325   To summarize, the DHCP service is handled by dnsmasq which is configured by Neutron to listen to the interface in the DHCP namespace. Neutron also configures dnsmasq with the combination of MAC and IP so when a DHCP request comes along it will receive the assigned IP. Summary In this post we relied on the components described in the previous post and saw how network connectivity is achieved using three simple use cases. These use cases gave a good view of the entire network stack and helped understand how an end to end connection is being made between a VM on a compute node and the DHCP namespace on the control node. One conclusion we can draw from what we saw here is that if we launch a VM and it is able to perform a DHCP request and receive a correct IP then there is reason to believe that the network is working as expected. We saw that a packet has to travel through a long list of components before reaching its destination and if it has done so successfully this means that many components are functioning properly. In the next post we will look at some more sophisticated services Neutron supports and see how they work. We will see that while there are some more components involved for the most part the concepts are the same. @RonenKofman

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  • Slow NFS and GFS2 performance

    - by Tiago
    Recently I've designed and configured a 4 node cluster for a webapp that does lots of file handling. The cluster have been broken down into 2 main roles, webserver and storage. Each role is replicated to a second server using drbd in active/passive mode. The webserver does a NFS mount of the data directory of the storage server and the latter also has a webserver running to serve files to browser clients. In the storage servers I've created a GFS2 FS to hold the data which is wired to drbd. I've chose GFS2 mainly because the announced performance and also because the volume size which has to be pretty high. Since we entered production I've been facing two problems that I think are deeply connected. First of all, the NFS mount on the webservers keeps hanging for a minute or so and then resumes normal operations. By analyzing the logs I've found out that NFS stops answering for a while and outputs the following log lines: Oct 15 18:15:42 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:44 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:46 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:47 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:47 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:47 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:48 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:48 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:51 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:52 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:52 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:55 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:55 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:58 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK In this case, the hang lasted for 16 seconds but sometimes it takes 1 or 2 minutes to resume normal operations. My first guess was this was happening due to heavy load of the NFS mount and that by increasing RPCNFSDCOUNT to a higher value, this would become stable. I've increased it several times and apparently, after a while, the logs started appearing less times. The value is now on 32. After further investigating the issue, I've came across a different hang, despite the NFS messages still appear in the logs. Sometimes, the GFS2 FS simply hangs which causes both the NFS and the storage webserver to serve files. Both stay hang for a while and then they resume normal operations. This hangs leaves no trace on client side (also leaves no NFS ... not responding messages) and, on the storage side, the log system appears to be empty, even though the rsyslogd is running. The nodes connect themselves through a 10Gbps non-dedicated connection but I don't think this is an issue because the GFS2 hang is confirmed but connecting directly to the active storage server. I've been trying to solve this for a while now and I've tried different NFS configuration options, before I've found out the GFS2 FS is also hanging. The NFS mount is exported as such: /srv/data/ <ip_address>(rw,async,no_root_squash,no_all_squash,fsid=25) And the NFS client mounts with: mount -o "async,hard,intr,wsize=8192,rsize=8192" active.storage.vlan:/srv/data /srv/data After some tests, these were the configurations that yielded more performance to the cluster. I am desperate to find a solution for this as the cluster is already in production mode and I need to fix this so that this hangs won't happen in the future and I don't really know for sure what and how I should be benchmarking. What I can tell is that this is happening due to heavy loads as I have tested the cluster earlier and this problems weren't happening at all. Please tell me if you need me to provide configuration details of the cluster, and which do you want me to post. As last resort I can migrate the files to a different FS but I need some solid pointers on whether this will solve this problems as the volume size is extremely large at this point. The servers are being hosted by a third-party enterprise and I don't have physical access to them. Best regards. EDIT 1: The servers are physical servers and their specs are: Webservers: Intel Bi Xeon E5606 2x4 2.13GHz 24GB DDR3 Intel SSD 320 2 x 120GB Raid 1 Storage: Intel i5 3550 3.3GHz 16GB DDR3 12 x 2TB SATA Initially there was a VRack setup between the servers but we've upgraded one of the storage servers to have more RAM and it wasn't inside the VRack. They connect through a shared 10Gbps connection between them. Please note that it is the same connection that is used for public access. They use a single IP (using IP Failover) to connect between them and to allow for a graceful failover. NFS is therefore over a public connection and not under any private network (it was before the upgrade, were the problem still existed). The firewall was configured and tested thoroughly but I disabled it for a while to see if the problem still occurred, and it did. From my knowledge the hosting provider isn't blocking or limiting the connection between either the servers and the public domain (at least under a given bandwidth consumption threshold that hasn't been reached yet). Hope this helps figuring out the problem. EDIT 2: Relevant software versions: CentOS 2.6.32-279.9.1.el6.x86_64 nfs-utils-1.2.3-26.el6.x86_64 nfs-utils-lib-1.1.5-4.el6.x86_64 gfs2-utils-3.0.12.1-32.el6_3.1.x86_64 kmod-drbd84-8.4.2-1.el6_3.elrepo.x86_64 drbd84-utils-8.4.2-1.el6.elrepo.x86_64 DRBD configuration on storage servers: #/etc/drbd.d/storage.res resource storage { protocol C; on <server1 fqdn> { device /dev/drbd0; disk /dev/vg_storage/LV_replicated; address <server1 ip>:7788; meta-disk internal; } on <server2 fqdn> { device /dev/drbd0; disk /dev/vg_storage/LV_replicated; address <server2 ip>:7788; meta-disk internal; } } NFS Configuration in storage servers: #/etc/sysconfig/nfs RPCNFSDCOUNT=32 STATD_PORT=10002 STATD_OUTGOING_PORT=10003 MOUNTD_PORT=10004 RQUOTAD_PORT=10005 LOCKD_UDPPORT=30001 LOCKD_TCPPORT=30001 (can there be any conflict in using the same port for both LOCKD_UDPPORT and LOCKD_TCPPORT?) GFS2 configuration: # gfs2_tool gettune <mountpoint> incore_log_blocks = 1024 log_flush_secs = 60 quota_warn_period = 10 quota_quantum = 60 max_readahead = 262144 complain_secs = 10 statfs_slow = 0 quota_simul_sync = 64 statfs_quantum = 30 quota_scale = 1.0000 (1, 1) new_files_jdata = 0 Storage network environment: eth0 Link encap:Ethernet HWaddr <mac address> inet addr:<ip address> Bcast:<bcast address> Mask:<ip mask> inet6 addr: <ip address> Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:957025127 errors:0 dropped:0 overruns:0 frame:0 TX packets:1473338731 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:2630984979622 (2.3 TiB) TX bytes:1648430431523 (1.4 TiB) eth0:0 Link encap:Ethernet HWaddr <mac address> inet addr:<ip failover address> Bcast:<bcast address> Mask:<ip mask> UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 The IP addresses are statically assigned with the given network configurations: DEVICE="eth0" BOOTPROTO="static" HWADDR=<mac address> ONBOOT="yes" TYPE="Ethernet" IPADDR=<ip address> NETMASK=<net mask> and DEVICE="eth0:0" BOOTPROTO="static" HWADDR=<mac address> IPADDR=<ip failover> NETMASK=<net mask> ONBOOT="yes" BROADCAST=<bcast address> Hosts file to allow for a graceful NFS failover in conjunction with NFS option fsid=25 set on both storage servers: #/etc/hosts <storage ip failover address> active.storage.vlan <webserver ip failover address> active.service.vlan As you can see, packet errors are down to 0. I've also ran ping for a long time without any packet loss. MTU size is the normal 1500. As there is no VLan by now, this is the MTU used to communicate between servers. The webservers' network environment is similar. One thing I forgot to mention is that the storage servers handle ~200GB of new files each day through the NFS connection, which is a key point for me to think this is some kind of heavy load problem with either NFS or GFS2. If you need further configuration details please tell me. EDIT 3: Earlier today we had a major filesystem crash on the storage server. I couldn't get the details of the crash right away because the server stop responding. After the reboot, I noticed the filesystem was extremely slow, and I was not being able to serve a single file through either NFS or httpd, perhaps due to cache warming or so. Nevertheless, I've been monitoring the server closely and the following error came up in dmesg. The source of the problem is clearly GFS, which is waiting for a lock and ends up starving after a while. INFO: task nfsd:3029 blocked for more than 120 seconds. "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. nfsd D 0000000000000000 0 3029 2 0x00000080 ffff8803814f79e0 0000000000000046 0000000000000000 ffffffff8109213f ffff880434c5e148 ffff880624508d88 ffff8803814f7960 ffffffffa037253f ffff8803815c1098 ffff8803814f7fd8 000000000000fb88 ffff8803815c1098 Call Trace: [<ffffffff8109213f>] ? wake_up_bit+0x2f/0x40 [<ffffffffa037253f>] ? gfs2_holder_wake+0x1f/0x30 [gfs2] [<ffffffff814ff42e>] __mutex_lock_slowpath+0x13e/0x180 [<ffffffff814ff2cb>] mutex_lock+0x2b/0x50 [<ffffffffa0379f21>] gfs2_log_reserve+0x51/0x190 [gfs2] [<ffffffffa0390da2>] gfs2_trans_begin+0x112/0x1d0 [gfs2] [<ffffffffa0369b05>] ? gfs2_dir_check+0x35/0xe0 [gfs2] [<ffffffffa0377943>] gfs2_createi+0x1a3/0xaa0 [gfs2] [<ffffffff8121aab1>] ? avc_has_perm+0x71/0x90 [<ffffffffa0383d1e>] gfs2_create+0x7e/0x1a0 [gfs2] [<ffffffffa037783f>] ? gfs2_createi+0x9f/0xaa0 [gfs2] [<ffffffff81188cf4>] vfs_create+0xb4/0xe0 [<ffffffffa04217d6>] nfsd_create_v3+0x366/0x4c0 [nfsd] [<ffffffffa0429703>] nfsd3_proc_create+0x123/0x1b0 [nfsd] [<ffffffffa041a43e>] nfsd_dispatch+0xfe/0x240 [nfsd] [<ffffffffa025a5d4>] svc_process_common+0x344/0x640 [sunrpc] [<ffffffff810602a0>] ? default_wake_function+0x0/0x20 [<ffffffffa025ac10>] svc_process+0x110/0x160 [sunrpc] [<ffffffffa041ab62>] nfsd+0xc2/0x160 [nfsd] [<ffffffffa041aaa0>] ? nfsd+0x0/0x160 [nfsd] [<ffffffff81091de6>] kthread+0x96/0xa0 [<ffffffff8100c14a>] child_rip+0xa/0x20 [<ffffffff81091d50>] ? kthread+0x0/0xa0 [<ffffffff8100c140>] ? child_rip+0x0/0x20

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  • .htaccess not working (mod_rewrite)

    - by Mike Curry
    Edit: I am pretty sure my .htaccess file is NOT being executed, and the problem is NOT with my rewrite rules. I have not having any luck getting my .htaccess with mod_rewrite working. Basically all I am trying to do is remove 'www' from "http://www.site.com" and "https://www.site.com". If there is anything I am missing (conf files, etc let me know I willl update this) I jsut can't see whats wrong here... I am using a 1&1 VPS III Virtual private server... anyone ever have this issue? I am using Ubuntu 8.04 Server LTS. Here is my .htaccess file (located @ /var/www/site/trunk/html/) Options +FollowSymLinks RewriteEngine on RewriteCond %{HTTP_HOST} ^www\.(.*) [NC] RewriteRule (.*) //%1/$1 [L,R=301] My mod_rewrite is enabled: The auto regenerated sym link is there in mods-available and /usr/lib/apache2/modules/ contains mod_rewrite.so root@s15348441:/etc/apache2/mods-available# more rewrite.load LoadModule rewrite_module /usr/lib/apache2/modules/mod_rewrite.so root@s15348441:/var/log# apache2ctl -t -D DUMP_MODULES Loaded Modules: core_module (static) log_config_module (static) logio_module (static) mpm_prefork_module (static) http_module (static) so_module (static) alias_module (shared) auth_basic_module (shared) authn_file_module (shared) authz_default_module (shared) authz_groupfile_module (shared) authz_host_module (shared) authz_user_module (shared) autoindex_module (shared) cgi_module (shared) dir_module (shared) env_module (shared) mime_module (shared) negotiation_module (shared) php5_module (shared) rewrite_module (shared) setenvif_module (shared) ssl_module (shared) status_module (shared) Syntax OK My apache config files: apache2.conf # # Based upon the NCSA server configuration files originally by Rob McCool. # # This is the main Apache server configuration file. It contains the # configuration directives that give the server its instructions. # See http://httpd.apache.org/docs/2.2/ for detailed information about # the directives. # # Do NOT simply read the instructions in here without understanding # what they do. They're here only as hints or reminders. If you are unsure # consult the online docs. You have been warned. # # The configuration directives are grouped into three basic sections: # 1. Directives that control the operation of the Apache server process as a # whole (the 'global environment'). # 2. Directives that define the parameters of the 'main' or 'default' server, # which responds to requests that aren't handled by a virtual host. # These directives also provide default values for the settings # of all virtual hosts. # 3. Settings for virtual hosts, which allow Web requests to be sent to # different IP addresses or hostnames and have them handled by the # same Apache server process. # # Configuration and logfile names: If the filenames you specify for many # of the server's control files begin with "/" (or "drive:/" for Win32), the # server will use that explicit path. If the filenames do *not* begin # with "/", the value of ServerRoot is prepended -- so "/var/log/apache2/foo.log" # with ServerRoot set to "" will be interpreted by the # server as "//var/log/apache2/foo.log". # ### Section 1: Global Environment # # The directives in this section affect the overall operation of Apache, # such as the number of concurrent requests it can handle or where it # can find its configuration files. # # # ServerRoot: The top of the directory tree under which the server's # configuration, error, and log files are kept. # # NOTE! If you intend to place this on an NFS (or otherwise network) # mounted filesystem then please read the LockFile documentation (available # at <URL:http://httpd.apache.org/docs-2.1/mod/mpm_common.html#lockfile>); # you will save yourself a lot of trouble. # # Do NOT add a slash at the end of the directory path. # ServerRoot "/etc/apache2" # # The accept serialization lock file MUST BE STORED ON A LOCAL DISK. # #<IfModule !mpm_winnt.c> #<IfModule !mpm_netware.c> LockFile /var/lock/apache2/accept.lock #</IfModule> #</IfModule> # # PidFile: The file in which the server should record its process # identification number when it starts. # This needs to be set in /etc/apache2/envvars # PidFile ${APACHE_PID_FILE} # # Timeout: The number of seconds before receives and sends time out. # Timeout 300 # # KeepAlive: Whether or not to allow persistent connections (more than # one request per connection). Set to "Off" to deactivate. # KeepAlive On # # MaxKeepAliveRequests: The maximum number of requests to allow # during a persistent connection. Set to 0 to allow an unlimited amount. # We recommend you leave this number high, for maximum performance. # MaxKeepAliveRequests 100 # # KeepAliveTimeout: Number of seconds to wait for the next request from the # same client on the same connection. # KeepAliveTimeout 15 ## ## Server-Pool Size Regulation (MPM specific) ## # prefork MPM # StartServers: number of server processes to start # MinSpareServers: minimum number of server processes which are kept spare # MaxSpareServers: maximum number of server processes which are kept spare # MaxClients: maximum number of server processes allowed to start # MaxRequestsPerChild: maximum number of requests a server process serves <IfModule mpm_prefork_module> StartServers 5 MinSpareServers 5 MaxSpareServers 10 MaxClients 150 MaxRequestsPerChild 0 </IfModule> # worker MPM # StartServers: initial number of server processes to start # MaxClients: maximum number of simultaneous client connections # MinSpareThreads: minimum number of worker threads which are kept spare # MaxSpareThreads: maximum number of worker threads which are kept spare # ThreadsPerChild: constant number of worker threads in each server process # MaxRequestsPerChild: maximum number of requests a server process serves <IfModule mpm_worker_module> StartServers 2 MaxClients 150 MinSpareThreads 25 MaxSpareThreads 75 ThreadsPerChild 25 MaxRequestsPerChild 0 </IfModule> # These need to be set in /etc/apache2/envvars User ${APACHE_RUN_USER} Group ${APACHE_RUN_GROUP} # # AccessFileName: The name of the file to look for in each directory # for additional configuration directives. See also the AllowOverride # directive. # AccessFileName .htaccess # # The following lines prevent .htaccess and .htpasswd files from being # viewed by Web clients. # <Files ~ "^\.ht"> Order allow,deny Deny from all </Files> # # DefaultType is the default MIME type the server will use for a document # if it cannot otherwise determine one, such as from filename extensions. # If your server contains mostly text or HTML documents, "text/plain" is # a good value. If most of your content is binary, such as applications # or images, you may want to use "application/octet-stream" instead to # keep browsers from trying to display binary files as though they are # text. # DefaultType text/plain # # HostnameLookups: Log the names of clients or just their IP addresses # e.g., www.apache.org (on) or 204.62.129.132 (off). # The default is off because it'd be overall better for the net if people # had to knowingly turn this feature on, since enabling it means that # each client request will result in AT LEAST one lookup request to the # nameserver. # HostnameLookups Off # ErrorLog: The location of the error log file. # If you do not specify an ErrorLog directive within a <VirtualHost> # container, error messages relating to that virtual host will be # logged here. If you *do* define an error logfile for a <VirtualHost> # container, that host's errors will be logged there and not here. # ErrorLog /var/log/apache2/error.log # # LogLevel: Control the number of messages logged to the error_log. # Possible values include: debug, info, notice, warn, error, crit, # alert, emerg. # LogLevel warn # Include module configuration: Include /etc/apache2/mods-enabled/*.load Include /etc/apache2/mods-enabled/*.conf # Include all the user configurations: Include /etc/apache2/httpd.conf # Include ports listing Include /etc/apache2/ports.conf # # The following directives define some format nicknames for use with # a CustomLog directive (see below). # If you are behind a reverse proxy, you might want to change %h into %{X-Forwarded-For}i # LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined LogFormat "%h %l %u %t \"%r\" %>s %b" common LogFormat "%{Referer}i -> %U" referer LogFormat "%{User-agent}i" agent # # ServerTokens # This directive configures what you return as the Server HTTP response # Header. The default is 'Full' which sends information about the OS-Type # and compiled in modules. # Set to one of: Full | OS | Minor | Minimal | Major | Prod # where Full conveys the most information, and Prod the least. # ServerTokens Full # # Optionally add a line containing the server version and virtual host # name to server-generated pages (internal error documents, FTP directory # listings, mod_status and mod_info output etc., but not CGI generated # documents or custom error documents). # Set to "EMail" to also include a mailto: link to the ServerAdmin. # Set to one of: On | Off | EMail # ServerSignature On # # Customizable error responses come in three flavors: # 1) plain text 2) local redirects 3) external redirects # # Some examples: #ErrorDocument 500 "The server made a boo boo." #ErrorDocument 404 /missing.html #ErrorDocument 404 "/cgi-bin/missing_handler.pl" #ErrorDocument 402 http://www.example.com/subscription_info.html # # # Putting this all together, we can internationalize error responses. # # We use Alias to redirect any /error/HTTP_<error>.html.var response to # our collection of by-error message multi-language collections. We use # includes to substitute the appropriate text. # # You can modify the messages' appearance without changing any of the # default HTTP_<error>.html.var files by adding the line: # # Alias /error/include/ "/your/include/path/" # # which allows you to create your own set of files by starting with the # /usr/share/apache2/error/include/ files and copying them to /your/include/path/, # even on a per-VirtualHost basis. The default include files will display # your Apache version number and your ServerAdmin email address regardless # of the setting of ServerSignature. # # The internationalized error documents require mod_alias, mod_include # and mod_negotiation. To activate them, uncomment the following 30 lines. # Alias /error/ "/usr/share/apache2/error/" # # <Directory "/usr/share/apache2/error"> # AllowOverride None # Options IncludesNoExec # AddOutputFilter Includes html # AddHandler type-map var # Order allow,deny # Allow from all # LanguagePriority en cs de es fr it nl sv pt-br ro # ForceLanguagePriority Prefer Fallback # </Directory> # # ErrorDocument 400 /error/HTTP_BAD_REQUEST.html.var # ErrorDocument 401 /error/HTTP_UNAUTHORIZED.html.var # ErrorDocument 403 /error/HTTP_FORBIDDEN.html.var # ErrorDocument 404 /error/HTTP_NOT_FOUND.html.var # ErrorDocument 405 /error/HTTP_METHOD_NOT_ALLOWED.html.var # ErrorDocument 408 /error/HTTP_REQUEST_TIME_OUT.html.var # ErrorDocument 410 /error/HTTP_GONE.html.var # ErrorDocument 411 /error/HTTP_LENGTH_REQUIRED.html.var # ErrorDocument 412 /error/HTTP_PRECONDITION_FAILED.html.var # ErrorDocument 413 /error/HTTP_REQUEST_ENTITY_TOO_LARGE.html.var # ErrorDocument 414 /error/HTTP_REQUEST_URI_TOO_LARGE.html.var # ErrorDocument 415 /error/HTTP_UNSUPPORTED_MEDIA_TYPE.html.var # ErrorDocument 500 /error/HTTP_INTERNAL_SERVER_ERROR.html.var # ErrorDocument 501 /error/HTTP_NOT_IMPLEMENTED.html.var # ErrorDocument 502 /error/HTTP_BAD_GATEWAY.html.var # ErrorDocument 503 /error/HTTP_SERVICE_UNAVAILABLE.html.var # ErrorDocument 506 /error/HTTP_VARIANT_ALSO_VARIES.html.var # Include of directories ignores editors' and dpkg's backup files, # see README.Debian for details. # Include generic snippets of statements Include /etc/apache2/conf.d/ # Include the virtual host configurations: Include /etc/apache2/sites-enabled/ My default config file for www on apache NameVirtualHost *:80 <VirtualHost *:80> ServerAdmin [email protected] #SSLEnable #SSLVerifyClient none #SSLCertificateFile /usr/local/ssl/crt/public.crt #SSLCertificateKeyFile /usr/local/ssl/private/private.key DocumentRoot /var/www/site/trunk/html <Directory /> Options FollowSymLinks AllowOverride all </Directory> <Directory /var/www/site/trunk/html> Options Indexes FollowSymLinks MultiViews AllowOverride all Order allow,deny allow from all </Directory> ScriptAlias /cgi-bin/ /usr/lib/cgi-bin/ <Directory "/usr/lib/cgi-bin"> AllowOverride None Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch Order allow,deny Allow from all </Directory> ErrorLog /var/log/apache2/error.log # Possible values include: debug, info, notice, warn, error, crit, # alert, emerg. LogLevel warn CustomLog /var/log/apache2/access.log combined ServerSignature On Alias /doc/ "/usr/share/doc/" <Directory "/usr/share/doc/"> Options Indexes MultiViews FollowSymLinks AllowOverride None Order deny,allow Deny from all Allow from 127.0.0.0/255.0.0.0 ::1/128 </Directory> </VirtualHost> My ssl config file NameVirtualHost *:443 <VirtualHost *:443> ServerAdmin [email protected] #SSLEnable #SSLVerifyClient none #SSLCertificateFile /usr/local/ssl/crt/public.crt #SSLCertificateKeyFile /usr/local/ssl/private/private.key DocumentRoot /var/www/site/trunk/html <Directory /> Options FollowSymLinks AllowOverride all </Directory> <Directory /var/www/site/trunk/html> Options Indexes FollowSymLinks MultiViews AllowOverride all Order allow,deny allow from all </Directory> ScriptAlias /cgi-bin/ /usr/lib/cgi-bin/ <Directory "/usr/lib/cgi-bin"> AllowOverride None Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch Order allow,deny Allow from all </Directory> ErrorLog /var/log/apache2/error.log # Possible values include: debug, info, notice, warn, error, crit, # alert, emerg. LogLevel warn SSLEngine On SSLCertificateFile /usr/local/ssl/crt/public.crt SSLCertificateKeyFile /usr/local/ssl/private/private.key CustomLog /var/log/apache2/access.log combined ServerSignature On Alias /doc/ "/usr/share/doc/" <Directory "/usr/share/doc/"> Options Indexes MultiViews FollowSymLinks AllowOverride None Order deny,allow Deny from all Allow from 127.0.0.0/255.0.0.0 ::1/128 </Directory> </VirtualHost> My /etc/apache2/httpd.conf is blank The directory /etc/apache2/conf.d has nothing in it but one file (charset) contents of /etc/apache2/conf.dcharset # Read the documentation before enabling AddDefaultCharset. # In general, it is only a good idea if you know that all your files # have this encoding. It will override any encoding given in the files # in meta http-equiv or xml encoding tags. #AddDefaultCharset UTF-8 My apache error.log [Wed Jun 03 00:12:31 2009] [error] [client 216.168.43.234] client sent HTTP/1.1 request without hostname (see RFC2616 section 14.23): /w00tw00t.at.ISC.SANS.DFind:) [Wed Jun 03 05:03:51 2009] [error] [client 99.247.237.46] File does not exist: /var/www/site/trunk/html/favicon.ico [Wed Jun 03 05:03:54 2009] [error] [client 99.247.237.46] File does not exist: /var/www/site/trunk/html/favicon.ico [Wed Jun 03 05:13:48 2009] [error] [client 99.247.237.46] File does not exist: /var/www/site/trunk/html/favicon.ico [Wed Jun 03 05:13:51 2009] [error] [client 99.247.237.46] File does not exist: /var/www/site/trunk/html/favicon.ico [Wed Jun 03 05:13:54 2009] [error] [client 99.247.237.46] File does not exist: /var/www/site/trunk/html/favicon.ico [Wed Jun 03 05:13:57 2009] [error] [client 99.247.237.46] File does not exist: /var/www/site/trunk/html/favicon.ico [Wed Jun 03 05:17:28 2009] [error] [client 99.247.237.46] File does not exist: /var/www/site/trunk/html/favicon.ico [Wed Jun 03 05:26:23 2009] [notice] caught SIGWINCH, shutting down gracefully [Wed Jun 03 05:26:34 2009] [notice] Apache/2.2.8 (Ubuntu) PHP/5.2.4-2ubuntu5.6 with Suhosin-Patch mod_ssl/2.2.8 OpenSSL/0.9.8g configured -- resuming normal operations [Wed Jun 03 06:03:41 2009] [notice] caught SIGWINCH, shutting down gracefully [Wed Jun 03 06:03:51 2009] [notice] Apache/2.2.8 (Ubuntu) PHP/5.2.4-2ubuntu5.6 with Suhosin-Patch mod_ssl/2.2.8 OpenSSL/0.9.8g configured -- resuming normal operations [Wed Jun 03 06:25:07 2009] [notice] caught SIGWINCH, shutting down gracefully [Wed Jun 03 06:25:17 2009] [notice] Apache/2.2.8 (Ubuntu) PHP/5.2.4-2ubuntu5.6 with Suhosin-Patch mod_ssl/2.2.8 OpenSSL/0.9.8g configured -- resuming normal operations [Wed Jun 03 12:09:25 2009] [error] [client 61.139.105.163] File does not exist: /var/www/site/trunk/html/fastenv [Wed Jun 03 15:04:42 2009] [notice] Graceful restart requested, doing restart [Wed Jun 03 15:04:43 2009] [notice] Apache/2.2.8 (Ubuntu) PHP/5.2.4-2ubuntu5.6 with Suhosin-Patch mod_ssl/2.2.8 OpenSSL/0.9.8g configured -- resuming normal operations [Wed Jun 03 15:29:51 2009] [error] [client 99.247.237.46] File does not exist: /var/www/site/trunk/html/favicon.ico [Wed Jun 03 15:29:54 2009] [error] [client 99.247.237.46] File does not exist: /var/www/site/trunk/html/favicon.ico [Wed Jun 03 15:30:32 2009] [error] [client 99.247.237.46] File does not exist: /var/www/site/trunk/html/favicon.ico [Wed Jun 03 15:45:54 2009] [notice] caught SIGWINCH, shutting down gracefully [Wed Jun 03 15:46:05 2009] [notice] Apache/2.2.8 (Ubuntu) PHP/5.2.4-2ubuntu5.6 with Suhosin-Patch mod_ssl/2.2.8 OpenSSL/0.9.8g configured -- resuming normal operations

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  • Windows Azure Use Case: Web Applications

    - by BuckWoody
    This is one in a series of posts on when and where to use a distributed architecture design in your organization's computing needs. You can find the main post here: http://blogs.msdn.com/b/buckwoody/archive/2011/01/18/windows-azure-and-sql-azure-use-cases.aspx  Description: Many applications have a requirement to be located outside of the organization’s internal infrastructure control. For instance, the company website for a brick-and-mortar retail company may want to post not only static but interactive content to be available to their external customers, and not want the customers to have access inside the organization’s firewall. There are also cases of pure web applications used for a great many of the internal functions of the business. This allows for remote workers, shared customer/employee workloads and data and other advantages. Some firms choose to host these web servers internally, others choose to contract out the infrastructure to an “ASP” (Application Service Provider) or an Infrastructure as a Service (IaaS) company. In any case, the design of these applications often resembles the following: In this design, a server (or perhaps more than one) hosts the presentation function (http or https) access to the application, and this same system may hold the computational aspects of the program. Authorization and Access is controlled programmatically, or is more open if this is a customer-facing application. Storage is either placed on the same or other servers, hosted within an RDBMS or NoSQL database, or a combination of the options, all coded into the application. High-Availability within this scenario is often the responsibility of the architects of the application, and by purchasing more hosting resources which must be built, licensed and configured, and manually added as demand requires, although some IaaS providers have a partially automatic method to add nodes for scale-out, if the architecture of the application supports it. Disaster Recovery is the responsibility of the system architect as well. Implementation: In a Windows Azure Platform as a Service (PaaS) environment, many of these architectural considerations are designed into the system. The Azure “Fabric” (not to be confused with the Azure implementation of Application Fabric - more on that in a moment) is designed to provide scalability. Compute resources can be added and removed programmatically based on any number of factors. Balancers at the request-level of the Fabric automatically route http and https requests. The fabric also provides High-Availability for storage and other components. Disaster recovery is a shared responsibility between the facilities (which have the ability to restore in case of catastrophic failure) and your code, which should build in recovery. In a Windows Azure-based web application, you have the ability to separate out the various functions and components. Presentation can be coded for multiple platforms like smart phones, tablets and PC’s, while the computation can be a single entity shared between them. This makes the applications more resilient and more object-oriented, and lends itself to a SOA or Distributed Computing architecture. It is true that you could code up a similar set of functionality in a traditional web-farm, but the difference here is that the components are built into the very design of the architecture. The API’s and DLL’s you call in a Windows Azure code base contains components as first-class citizens. For instance, if you need storage, it is simply called within the application as an object.  Computation has multiple options and the ability to scale linearly. You also gain another component that you would either have to write or bolt-in to a typical web-farm: the Application Fabric. This Windows Azure component provides communication between applications or even to on-premise systems. It provides authorization in either person-based or claims-based perspectives. SQL Azure provides relational storage as another option, and can also be used or accessed from on-premise systems. It should be noted that you can use all or some of these components individually. Resources: Design Strategies for Scalable Active Server Applications - http://msdn.microsoft.com/en-us/library/ms972349.aspx  Physical Tiers and Deployment  - http://msdn.microsoft.com/en-us/library/ee658120.aspx

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  • How do NTP Servers Manage to Stay so Accurate?

    - by Akemi Iwaya
    Many of us have had the occasional problem with our computers and other devices retaining accurate time settings, but a quick sync with an NTP server makes all well again. But if our own devices can lose accuracy, how do NTP servers manage to stay so accurate? Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites. Photo courtesy of LEOL30 (Flickr). The Question SuperUser reader Frank Thornton wants to know how NTP servers are able to remain so accurate: I have noticed that on my servers and other machines, the clocks always drift so that they have to sync up to remain accurate. How do the NTP server clocks keep from drifting and always remain so accurate? How do the NTP servers manage to remain so accurate? The Answer SuperUser contributor Michael Kjorling has the answer for us: NTP servers rely on highly accurate clocks for precision timekeeping. A common time source for central NTP servers are atomic clocks, or GPS receivers (remember that GPS satellites have atomic clocks onboard). These clocks are defined as accurate since they provide a highly exact time reference. There is nothing magical about GPS or atomic clocks that make them tell you exactly what time it is. Because of how atomic clocks work, they are simply very good at, having once been told what time it is, keeping accurate time (since the second is defined in terms of atomic effects). In fact, it is worth noting that GPS time is distinct from the UTC that we are more used to seeing. These atomic clocks are in turn synchronized against International Atomic Time or TAI in order to not only accurately tell the passage of time, but also the time. Once you have an exact time on one system connected to a network like the Internet, it is a matter of protocol engineering enabling transfer of precise times between hosts over an unreliable network. In this regard a Stratum 2 (or farther from the actual time source) NTP server is no different from your desktop system syncing against a set of NTP servers. By the time you have a few accurate times (as obtained from NTP servers or elsewhere) and know the rate of advancement of your local clock (which is easy to determine), you can calculate your local clock’s drift rate relative to the “believed accurate” passage of time. Once locked in, this value can then be used to continuously adjust the local clock to make it report values very close to the accurate passage of time, even if the local real-time clock itself is highly inaccurate. As long as your local clock is not highly erratic, this should allow keeping accurate time for some time even if your upstream time source becomes unavailable for any reason. Some NTP client implementations (probably most ntpd daemon or system service implementations) do this, and others (like ntpd’s companion ntpdate which simply sets the clock once) do not. This is commonly referred to as a drift file because it persistently stores a measure of clock drift, but strictly speaking it does not have to be stored as a specific file on disk. In NTP, Stratum 0 is by definition an accurate time source. Stratum 1 is a system that uses a Stratum 0 time source as its time source (and is thus slightly less accurate than the Stratum 0 time source). Stratum 2 again is slightly less accurate than Stratum 1 because it is syncing its time against the Stratum 1 source and so on. In practice, this loss of accuracy is so small that it is completely negligible in all but the most extreme of cases. Have something to add to the explanation? Sound off in the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.

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  • Install Oracle Configuration Manager's Standalone Collector

    - by Get Proactive Customer Adoption Team
    Untitled Document The Why and the How If you have heard of Oracle Configuration Manager (OCM), but haven’t installed it, I’m guessing this is for one of two reasons. Either you don’t know how it helps you or you don’t know how to install it. I’ll address both of those reasons today. First, let’s take a quick look at how My Oracle Support and the Oracle Configuration Manager work together to gain a good understanding of what their differences and roles are before we tackle the install.   Oracle Configuration Manger is the tool that actually performs the data collection task. You deploy this lightweight piece of software into your system to collect configuration information about the system and OCM uploads that data to Oracle’s customer configuration repository. Oracle Support Engineers then have the configuration data available when you file a service request. You can also view the data through My Oracle Support. The real value is that the data Oracle Configuration Manager collects can help you avoid problems and get your Service Requests solved more quickly. When you view the information in My Oracle Support’s user interface to OCM, it may help you avoid situations that create problems. The proactive tools included in Oracle Configuration Manager help you avoid issues before they occur. You also save time because you didn’t need to open a service request. For example, you can use this capability when you need to compare your system configuration at two points in time, or monitor the system health. If you make the configuration data available to Oracle Support Engineers, when you need to open a Service Request the data helps them diagnose and resolve your critical system issues more quickly, which means you get answers more quickly too. Quick Installation Process Overview Before we dive into the step-by-step details, let me provide a quick overview. For some of you, this will be all you need. Log in to My Oracle Support and download the data collector from Collector tab. If you don’t see the Collector tab, click the More tab gain access. On the Collector tab, you will find a drop-down list showing which platforms are available. You can also see more ways to the Collector can help you if you click through the carousel of benefits. After you download the software for your platform, use FTP to move that file (.zip) from your PC to the server that hosts the Oracle software. Once you have that file on the server, locate the $ORACLE_HOME directory, and unzip the file within that directory. You can then use the command line tool to start the installation process. The installation process requires the My Oracle Support credential (Support Identifier, username, and password) Proxy specification (Host IP Address, Port number, username and password) Installation Step-by-Step Download the collector zip file from My Oracle Support and place it into your $Oracle_Home Unzip the zip file you downloaded from My Oracle Support – this will create a directory named CCR with several subdirectories Using the command line go to “$ORACLE_HOME/CCR/bin” and run the following command “setupCCR” Provide your My Oracle Support credential: login, password, and Support Identifier The installer will start deploying the collector application You have installed the Collector Post Installation Now that you have installed successfully, the scheduler is ready to collect configuration information for the software available in your Oracle Home. By default, the first collection will take place the day after the installation. If you want to run an instrumentation script to start the configuration collection of your Oracle Database server, E-Business Suite, or Enterprise Manager, you will find more details on that in the Installation and Administration Guide for My Oracle Support Configuration Manager. Related documents available on My Oracle Support Oracle Configuration Manager Installation and Administration Guide [ID 728989.5] Oracle Configuration Manager Prerequisites [ID 728473.5] Oracle Configuration Manager Network Connectivity Test [ID 728970.5] Oracle Configuration Manager Collection Overview [ID 728985.5] Oracle Configuration Manager Security Overview [ID 728982.5] Oracle Software Configuration Manager: Disconnected Mode Collection [ID 453412.1]

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