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  • Learn Many Languages

    - by Phil Factor
    Around twenty-five years ago, I was trying to solve the problem of recruiting suitable developers for a large business. I visited the local University (it was a Technical College then). My mission was to remind them that we were a large, local employer of technical people and to suggest that, as they were in the business of educating young people for a career in IT, we should work together. I anticipated a harmonious chat where we could suggest to them the idea of mentioning our name to some of their graduates. It didn’t go well. The academic staff displayed a degree of revulsion towards the whole topic of IT in the world of commerce that surprised me; tweed met charcoal-grey, trainers met black shoes. However, their antipathy to commerce was something we could have worked around, since few of their graduates were destined for a career as university lecturers. They asked me what sort of language skills we needed. I tried ducking the invidious task of naming computer languages, since I wanted recruits who were quick to adapt and learn, with a broad understanding of IT, including development methodologies, technologies, and data. However, they pressed the point and I ended up saying that we needed good working knowledge of C and BASIC, though FORTRAN and COBOL were, at the time, still useful. There was a ghastly silence. It was as if I’d recommended the beliefs and practices of the Bogomils of Bulgaria to a gathering of Cardinals. They stared at me severely, like owls, until the head of department broke the silence, informing me in clipped tones that they taught only Modula 2. Now, I wouldn’t blame you if at this point you hurriedly had to look up ‘Modula 2′ on Wikipedia. Based largely on Pascal, it was a specialist language for embedded systems, but I’ve never ever come across it in a commercial business application. Nevertheless, it was an excellent teaching language since it taught modules, scope control, multiprogramming and the advantages of encapsulating a set of related subprograms and data structures. As long as the course also taught how to transfer these skills to other, more useful languages, it was not necessarily a problem. I said as much, but they gleefully retorted that the biggest local employer, a defense contractor specializing in Radar and military technology, used nothing but Modula 2. “Why teach any other programming language when they will be using Modula 2 for all their working lives?” said a complacent lecturer. On hearing this, I made my excuses and left. There could be no meeting of minds. They were providing training in a specific computer language, not an education in IT. Twenty years later, I once more worked nearby and regularly passed the long-deserted ‘brownfield’ site of the erstwhile largest local employer; the end of the cold war had led to lean times for defense contractors. A digger was about to clear the rubble of the long demolished factory along with the accompanying growth of buddleia and thistles, in order to lay the infrastructure for ‘affordable housing’. Modula 2 was a distant memory. Either those employees had short working lives or they’d retrained in other languages. The University, by contrast, was thriving, but I wondered if their erstwhile graduates had ever cursed the narrow specialization of their training in IT, as they struggled with the unexpected variety of their subsequent careers.

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  • Whats the best way to update Ubuntu 9.04?

    - by Fu86
    I have a Ubuntu 9.04 server which has no packase support anymore. If I want to update my package lists, I get th following errors: Err http://de.archive.ubuntu.com jaunty-security/multiverse Packages 404 Not Found [IP: 141.30.13.10 80] W: Failed to fetch http://de.archive.ubuntu.com/ubuntu/dists/jaunty/main/binary-amd64/Packages 404 Not Found [IP: 141.30.13.10 80] .... I read at the official Ubuntu-Support-Page, that there is a update-manager-core-Package to upgrade to a new release. Unfortunately I dont have this package installed and I am unable to install it because of the lack of package sources. EDIT: Installing the package update-manager-core from another release doesn't work because it depends on a higher version of python-apt. (Tried with 10.04) $ dpkg -i update-manager-core_0.134.7_amd64.deb Selecting previously deselected package update-manager-core. (Reading database ... 28743 files and directories currently installed.) Unpacking update-manager-core (from update-manager-core_0.134.7_amd64.deb) ... dpkg: dependency problems prevent configuration of update-manager-core: update-manager-core depends on python-apt (>= 0.7.13.4ubuntu3); however: Version of python-apt on system is 0.7.9~exp2ubuntu10. update-manager-core depends on python-gnupginterface; however: Package python-gnupginterface is not installed. dpkg: error processing update-manager-core (--install): dependency problems - leaving unconfigured Errors were encountered while processing: update-manager-core So, whats the best way to upgrade to to current Release without reinstalling the complete (virtual) server?

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  • No apparent reason for high load average

    - by Oz.
    We have several web servers running on Amazon (ec2) c1.xlarge, over Amazon AMI. The servers are duplicates of each other, running the exact same hardware and software. Each server spec is: 7 GB of memory 20 EC2 Compute Units (8 virtual cores with 2.5 EC2 Compute Units each) 1690 GB of instance storage 64-bit platform I/O Performance: High API name: c1.xlarge A couple of weeks ago we have run a yum upgrade on one of the servers. Starting on this upgrade the upgraded server started showing a high load average. Needless to say, we did not update the other servers and we can not do so until we understand the reason for this behavior. The strange thing is that when we compare the servers using top or iostat, we can not find the reason for the high load. Note that we have moved traffic from the "problematic" server to the others, which have made the "problematic" server less crowded in terms of requests, and still his load is higher. Do you have any idea what could it be, or where else can we check? Many thanks for the help! Oz. # # proper server # w command # 00:42:26 up 2 days, 19:54, 2 users, load average: 0.41, 0.48, 0.49 USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT pts/1 82.80.137.29 00:28 14:05 0.01s 0.01s -bash pts/2 82.80.137.29 00:38 0.00s 0.02s 0.00s w # # proper server # iostat command # Linux 3.2.12-3.2.4.amzn1.x86_64 _x86_64_ (8 CPU) avg-cpu: %user %nice %system %iowait %steal %idle 9.03 0.02 4.26 0.17 0.13 86.39 Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn xvdap1 1.63 1.50 55.00 367236 13444008 xvdfp1 4.41 45.93 70.48 11227226 17228552 xvdfp2 2.61 2.01 59.81 491890 14620104 xvdfp3 8.16 14.47 94.23 3536522 23034376 xvdfp4 0.98 0.79 45.86 192818 11209784 # # problematic server # w command # 00:43:26 up 2 days, 21:52, 2 users, load average: 1.35, 1.10, 1.17 USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT pts/0 82.80.137.29 00:28 15:04 0.02s 0.02s -bash pts/1 82.80.137.29 00:38 0.00s 0.05s 0.00s w # # problematic server # iostat command # Linux 3.2.20-1.29.6.amzn1.x86_64 _x86_64_ (8 CPU) avg-cpu: %user %nice %system %iowait %steal %idle 7.97 0.04 3.43 0.19 0.07 88.30 Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn xvdap1 2.10 1.49 76.54 374660 19253592 xvdfp1 5.64 40.98 85.92 10308946 21612112 xvdfp2 3.97 4.32 93.18 1087090 23439488 xvdfp3 10.87 30.30 115.14 7622474 28961720 xvdfp4 1.12 0.28 65.54 71034 16487112

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  • HyperV - low CPU usage

    - by Klark
    I am very new to HyperV and virtual machine philosophy in general, so please expect more or less nooby questions :) I have a server that is only used as a host for virtual machines. OS is windows server 2008 R2 and it is running on 16 CPU and 48 GBs of RAM. On aforementioned server there are 8 VMs, each having 4 CPUs and 4 GBs of RAM. On those VMs we are running some CPU intensive tasks. Each machine has nearly 100% cpu usage. After I noticed slow performance I went to the host machine and started playing with process explorer. It turned out that cpu usage is very low. Also I/O is very low, and of course, memory consumption is high, which is expected. Of course, I don't expect that those 4 virtual cores dedicated to a VM work as fast as real, hardware 4 cores, but still I expected a higher consumption of real hardware. Is this sort of behaviour normal? I see that the most of CPU usage on host machine are marked as interrupts (which I guess is normal) and all those interrupts are passed to only one core (which is strange). Are there out of box optimization that I could perform to finally use all that processing power that is under the hood. My knowledge of virtualization technology is near to embarrassing, so I would be grateful for any links that could enlightened me :) Thanks.

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  • ASP.NET Session State SQL Server 2008 R2 Freezes with High CPU Usage

    - by jtseng
    Our ASP.Net website uses SQL Server as the session state provider. We currently host the database on SQL Server 2005 since it does not play well on 2008 R2. We would like to know why, and how to fix it. hardware setup Our current session state server has SQL Server 2005 with the files hosted on a single local disk. It is one of our oldest servers since it has served us well, and we never felt the need to upgrade it. The database is about 2 GB holding 6000 sessions. (The sessions are a little big, but we need it.) We have another server with SQL Server 2008 R2 with a much faster CPU, much more RAM, and a much faster hard disk. situation One day, we have a huge surge in traffic. The transaction log growth on SQL Server freezes the server for 10's of seconds, allowing only a few requests through in minutes. So we load up the new server with ASPState with very large data and log files and point all of our applications to the new server. It chugs along fine for about 5 minutes, and then the CPU usage jumps up to 50% of the 16 cores that Standard Edition can use and freezes for 10's of seconds at a time. The files do not record any autogrowth events. The disk queue is nice and low. RAM usage is low. CPU usage on our old server has never been higher than 5%. What happened on the new server? Alternatively, I would like to hear success stories with ASP.NET session state server running on SQL Server 2008 R2 with an average write load of 30MB/sec with bursts up to 200MB/sec.

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  • Problem routing between directly connected Subnets w/ ASA-5510

    - by Zephyr Pellerin
    This is an issue I've been struggling with for quite some time, with a seemingly simple answer (Aren't all IT problems?). And that is the problem of passing traffic between two directly connected subnets with an ASA While I'm aware that best practice is to have Internet - Firewall - Router, in many cases this isn't possible. For example, In have an ASA with two interfaces, named OutsideNetwork (10.19.200.3/24) and InternalNetwork (10.19.4.254/24). You'd expect Outside to be able to get to, say, 10.19.4.1, or at LEAST 10.19.4.254, but pinging the interface gives only bad news. Result of the command: "ping OutsideNetwork 10.19.4.254" Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 10.19.4.254, timeout is 2 seconds: ????? Success rate is 0 percent (0/5) Naturally, you'd assume that you could add a static route, to no avail. [ERROR] route Outsidenetwork 10.19.4.0 255.255.255.0 10.19.4.254 1 Cannot add route, connected route exists At this point, you might gander if its a NAT or Access list problem. access-list Outsidenetwork_access_in extended permit ip any any access-list Internalnetwork_access_in extended permit ip any any There is no dynamic nat (or static nat for that matter), and Unnatted traffic is permitted. When I try pinging the above address (10.19.4.254 from Outsidenetwork), I get this error message from level 0 logging (debugging). Routing failed to locate next hop for icmp from NP Identity Ifc:10.19.200.3/0 to Outsidenetwork:10.19.4.1/0 This led me to set same-security traffic permit, and assigned the same, lesser and greater security numbers between the two interfaces. Am I overlooking something obvious? Is there a command to set static routes that are classified higher than connected routes?

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  • How can I configure multiple default gateways on a CISCO Router?

    - by Spirit
    Does any one knows a way to configure a cisco router with multiple gateways - multiple gateways of last resort? I've tried adding a gateway of last resort twice (with different metric) but only one is shown: Router(config)# ip route 0.0.0.0 0.0.0.0 2.2.2.2 10 Router(config)# ip route 0.0.0.0 0.0.0.0 3.3.3.3 100 And the show ip route output was: Router# show ip route Gateway of last resort is 2.2.2.2 to network 0.0.0.0 2.0.0.0/24 is subnetted, 1 subnets C 2.2.2.0 is directly connected, FastEthernet0/0 3.0.0.0/24 is subnetted, 1 subnets C 3.3.3.0 is directly connected, FastEthernet0/1 32.0.0.0/30 is subnetted, 1 subnets C 32.2.2.0 is directly connected, Serial0/2/0 S* 0.0.0.0/0 [10/0] via 2.2.2.2 The point is that i cannot see the other route with higher distance metric? Anyone has a sugestion? I mean will this config work if the link on 2.2.2.2 fails? Will the router choose the other network 3.3.3.3, if the link 2.2.2.2 fails?

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  • Adventures in Drupal multisite config with mod_rewrite and clean urls

    - by moexu
    The university where I work is planning to offer Drupal hosting to staff/faculty who want a Drupal site. We've set up Drupal multisite with clean urls and it's mostly working except for some weird redirects. If you have two sites where one is a substring of the other then you'll randomly be redirected to the other site. I tracked the problem to how mod_rewrite does path matching, so with a config file like this: RewriteCond %{REQUEST_URI} ^/drupal RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteRule ^(.*)$ /drupal/index.php?q=$1 [last,qsappend] RewriteCond %{REQUEST_URI} ^/drupaltest RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteRule ^(.*)$ /drupaltest/index.php?q=$1 [last,qsappend] /drupaltest will match the /drupal line and all of the links on the /drupaltest page will be rewritten to point to /drupal. If you put the end of string character ($) at the end of each rewrite condition then it will always match on the correct site and the links will always be rewritten correctly. That breaks down as soon as a user logs in though because the query string is appended to the url so just the base url will no longer match. You can also fix the problem by ordering the sites in the config file so that the smallest substring will always be last. I suggested storing all of the sites in a table and then querying, sorting, and rewriting the config file every time a Drupal site is requested so that we could guarantee the order. The system administrator thought that was kludgy and didn't address the root problem. Disabling clean urls should also fix the problem but the users really want them so I'd prefer to keep them if possible. I think we could also fix it by using an .htaccess file in each site to handle the clean url rewriting but that also seems suboptimal since it will generate a higher load on the server and the server is intended to host the majority of the university's external facing web content. Is there some magic I can do with mod_rewrite to get it to work? Would another solution be better? Am I doing something the wrong way to begin with?

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  • What's needed in a complete ASP.NET environment?

    - by Christian W
    We have a ASP3.0 application with a few ASP.NET (2.0) dittys mixed in. (Our longtime goal is to migrate everything to ASP.NET but that's not important for this issue) Our current test/deploy workflow is like this: 1 Use notepad++ or VS2008 to fix a bug/feature (depending on what I have open) 2 Open my virtual test-server 3 Copy the fixed file over, either with explorer, or if I can be bothered to open it, WinMerge 4 Test that the fix works 5 Close the virtual test-server 6 Connect to our host with VPN 7 Use WinMerge to update the files necessary 8 Pray to higher powers that the production environment is not so different that something bombs. To make things worse, only I have access to my "test-server". So I'm the only one testing it. I really want to make this a bit more robust, I even have a subversion setup running. But I always forget to commit changes... And I don't even work in my checked out folder, but a copy of what is currently in production... Can someone recommend some good reading on deploying, testing, staging and stuff like that. I currently use VS2008 and want to use subversion or GIT (or any other free VCS). Since I'm the only developer, teamsystem is not really an option (cost-related). I have found myself developing an "improved" feature, only to find a bug in the same feature in the production system. And since my "improved" feature incorporated deleting some old functionality, I have to fix bugs directly in production... That's not a fun feeling... (I have inherited this system recently... So it's not directly my fault that it is like this ;) )

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  • Fun with Python

    - by dotneteer
    I am taking a class on Coursera recently. My formal education is in physics. Although I have been working as a developer for over 18 years and have learnt a lot of programming on the job, I still would like to gain some systematic knowledge in computer science. Coursera courses taught by Standard professors provided me a wonderful chance. The three languages recommended for assignments are Java, C and Python. I am fluent in Java and have done some projects using C++/MFC/ATL in the past, but I would like to try something different this time. I first started with pure C. Soon I discover that I have to write a lot of code outside the question that I try to solve because the very limited C standard library. For example, to read a list of values from a file, I have to read characters by characters until I hit a delimiter. If I need a list that can grow, I have to create a data structure myself, something that I have taking for granted in .Net or Java. Out of frustration, I switched to Python. I was pleasantly surprised to find that Python is very easy to learn. The tutorial on the official Python site has the exactly the right pace for me, someone with experience in another programming. After a couple of hours on the tutorial and a few more minutes of toying with IDEL, I was in business. I like the “battery supplied” philosophy that gives everything that I need out of box. For someone from C# or Java background, curly braces are replaced by colon(:) and tab spaces. Although I tend to miss colon from time to time, I found that the idea of tab space is actually very nice once I get use to them. I also like to feature of multiple assignment and multiple return parameters. When I need to return a by-product, I just add it to the list of returns. When would use Python? I would use Python if I need to computer anything quick. The language is very easy to use. Python has a good collection of libraries (packages). The REPL of the interpreter allows me test ideas quickly before committing them into script. Lots of computer science work have been ported from Lisp to Python. Some universities are even teaching SICP in Python. When wouldn’t I use Python? I mostly would not use it in a managed environment, such as Ironpython or Jython. Both .Net and Java already have a rich library so one has to make a choice which library to use. If we use the managed runtime library, the code will tie to the particular runtime and thus not portable. If we use the Python library, then we will face the relatively long start-up time. For this reason, I would not recommend to use Ironpython for WP7 development. The only situation that I see merit with managed Python is in a server application where I can preload Python so that the start-up time is not a concern. Using Python as a managed glue language is an over-kill most of the time. A managed Scheme could be a better glue language as it is small enough to start-up very fast.

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  • Why does my exchange message filtering rule not work?

    - by Jon Cage
    I have two rules set up to sort incoming bug reports. The first is specific to a single device: Apply this rule after the message arrives sent to SMS Distribution and with <source_device_number>: in the body move it to the BugReports\<source_device_number> folder ..and the second is a catch-all for everything else: Apply this rule after the message arrives sent to SMS Distribution move it to the BugReports folder For some reason though, the first rule never seems to act even though it's higher in the list. So for some reason an email like the following doesn't seem to get caught by the first rule: From: <SourceDeviceUID> To: SMS Distributor Subject: Message from <SourceDeviceUID> Message: <source_device_number>: Device encountered a problem. Details below... ...where <source_device_number> is an integer. The second rule works fine. But for some high-priority devices, I want them automatically sorted. Why might that first rule fail?

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  • Debian x86_64 + Nginx + PHP5-FPM optimization

    - by Olal'a
    I used to have a VPS (512MB) from Linode and I was running nginx + php5-fpm (which comes with php5.3.3) on Debian Lenny (i686). The total memory usage was about 90-100MB. Now I have another VPS (different hosting company) and I also run nginx + php5-fpm on Debian Lenny (x86_64). The system is 64-bit, so the memory usage is higher now, about 210-230MB, which I think is too much. Here is my php5-fpm.conf: pm = dynamic pm.max_children = 5 pm.start_servers = 2 pm.min_spare_servers = 2 pm.max_spare_servers = 5 pm.max_requests = 300 That's what top command tells me: top - 15:36:58 up 3 days, 16:05, 1 user, load average: 0.00, 0.00, 0.00 Tasks: 209 total, 1 running, 208 sleeping, 0 stopped, 0 zombie Cpu(s): 0.0%us, 0.0%sy, 0.0%ni, 99.9%id, 0.1%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 532288k total, 469628k used, 62660k free, 28760k buffers Swap: 1048568k total, 408k used, 1048160k free, 210060k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 22806 www-data 20 0 178m 67m 31m S 1 13.1 0:05.02 php5-fpm 8980 mysql 20 0 241m 55m 7384 S 0 10.6 2:42.42 mysqld 22807 www-data 20 0 162m 43m 22m S 0 8.3 0:04.84 php5-fpm 22808 www-data 20 0 160m 41m 23m S 0 8.0 0:04.68 php5-fpm 25102 www-data 20 0 151m 30m 21m S 0 5.9 0:00.80 php5-fpm 10849 root 20 0 44100 8352 1808 S 0 1.6 0:03.16 munin-node 22805 root 20 0 145m 4712 1472 S 0 0.9 0:00.16 php5-fpm 21859 root 20 0 66168 3248 2540 S 1 0.6 0:00.02 sshd 21863 root 20 0 66028 3188 2548 S 0 0.6 0:00.06 sshd 3956 www-data 20 0 31756 3052 928 S 0 0.6 0:06.42 nginx 3954 www-data 20 0 31712 3036 928 S 0 0.6 0:06.74 nginx 3951 www-data 20 0 31712 3008 928 S 0 0.6 0:06.42 nginx 3957 www-data 20 0 31688 2992 928 S 0 0.6 0:06.56 nginx 3950 www-data 20 0 31676 2980 928 S 0 0.6 0:06.72 nginx 3955 www-data 20 0 31552 2896 928 S 0 0.5 0:06.56 nginx 3953 www-data 20 0 31552 2888 928 S 0 0.5 0:06.42 nginx 3952 www-data 20 0 31544 2880 928 S 0 0.5 0:06.60 nginx So, the question is there any way to use less memory? Btw, I have 16 cores and it would be nice to make use of them...

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  • limiting connections from tomcat to IIS - proxy? iptables?

    - by Chris Phillips
    Howdy, I've webapp on tomcat6 which is connecting to an M$ PlayReady DRM instance on IIS6.0 The performance is seen to be best when we bench mark (using ab) the DRM service with 25 concurrent connections, which gives about 250 requests per second, which is ace. higher concurrent connections results in TCP/IP timeouts and other lower level mess. But there is no way to control how the tomcat app connects to the service - it's not internally managing a pool of connections etc, they are all isolated http connections to the server. Ideally I'd like a situation where we can have 25 http 1.1 connections being kept alive permanently from tomcat and requesting the licenses through this static pool of connections, which I think would the best performance. But this is not in the code, so was looking for a way to possibly simulate this at the Linux level. I was possibly thinking that iptables connlimit might be able to gracefully handle these connections, but whilst it could limit, it'd probably still annoy the app. What about a proxy? nginx (or possibly squid) seems potentially appealing to run on the tomcat server and hit on localhost as we might want to add additional DRM servers to use under load balance anyway. Could this take 100 incoming connections from tomcat, accept them all and proxy over the the IIS server in a more respectful manner? Any other angles? EDIT - looking over mod_proxy for apache, which we are already using for conventional use on an apache instance in front of this tomcat instance, might be ideal. I can set a max value on the proxy_pass to only allow 25 connections, and keep them alive permanently. Is that my answer? Many thanks, Chris

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  • mysql thread count

    - by Ryan M.
    We have a web application that uses apache and mysql. Generally (according to Munin) our MySQL thread count sits between 2 and 4 at all times. The other day, our server almost came to a halt. HTTP requests were slow or wouldn't go through at all, SSH would work, but would take 30+ seconds to register keystrokes, etc.. So we pull up Munin and the only thing that's out of normal boundaries is the Mysql thread count. CPU usage was under 1%, load was under 1.0, plenty of available RAM. As mentioned before, the thread count floats around 2 to 4. At the time of our slow downs it had spiked to 14. So I start poking around the Internet and I see that in most cases, you'll start to see a higher thread count when you start running into slow queries. If I understand it correctly, the request comes in that takes a while to process, in the mean time other requests are coming in, so a new thread will be created to work on the request (yes?). But at the time of the slow down, we had 0 slow queries. My question is: What else can cause mysql to create additional threads. And would this sudden spike in threads possibly cause the server to slow down? To fix the issue, we restarted apache and everything went back to it's beautiful, normal self. Considering the the Server Vitals (CPU, RAM, Network, etc) were all ideal, and the thread count was the only thing out of place, this seems like the most logical thing to pursue as the possible cause. If it matters, we're on Mysql 5.1.40. Server is FreeBSD 7.2 and the server in question is inside a jail.

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  • Understanding RedHats recommended tuned profiles

    - by espenfjo
    We are going to roll out tuned (and numad) on ~1000 servers, the majority of them being VMware servers either on NetApp or 3Par storage. According to RedHats documentation we should choose the virtual-guestprofile. What it is doing can be seen here: tuned.conf We are changing the IO scheduler to NOOP as both VMware and the NetApp/3Par should do sufficient scheduling for us. However, after investigating a bit I am not sure why they are increasing vm.dirty_ratio and kernel.sched_min_granularity_ns. As far as I have understood increasing increasing vm.dirty_ratio to 40% will mean that for a server with 20GB ram, 8GB can be dirty at any given time unless vm.dirty_writeback_centisecsis hit first. And while flushing these 8GB all IO for the application will be blocked until the dirty pages are freed. Increasing the dirty_ratio would probably mean higher write performance at peaks as we now have a larger cache, but then again when the cache fills IO will be blocked for a considerably longer time (Several seconds). The other is why they are increasing the sched_min_granularity_ns. If I understand it correctly increasing this value will decrease the number of time slices per epoch(sched_latency_ns) meaning that running tasks will get more time to finish their work. I can understand this being a very good thing for applications with very few threads, but for eg. apache or other processes with a lot of threads would this not be counter-productive?

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  • VLAN ACLs and when to go Layer 3

    - by wuckachucka
    I want to: a) segment several departments into VLANs with the hopes of restricting access between them completely (Sales never needs to talk to Support's workstations or printers and vice-versa) or b) certain IP addresses and TCP/UDP ports across VLANS -- i.e. permitting the Sales VLAN to access the CRM Web Server in the Server VLAN on port 443 only. Port-wise, I'll need a 48-port switch and another 24-port switch to go with the two existing 24-port Layer 2 switches (Linksys); I'm looking at going with D-Links or HP Procurves as Cisco is out of our price range. Question #1: From what I understand (and please correct me if I'm wrong), if the Servers (VLAN10) and Sales (VLAN20) are all on the same 48-port switch (or two stacked 24-port switches), afaik, the switch "knows" what VLANs and ports each device belongs to and will switch packets between them; I can also apply ACLs to restrict access between VLANs at this point. Is this correct? Question #2: Now lets say that Support (VLAN30) is on a different switch (one of the Linksys) switches. I'm assuming I'll need to trunk (tag) switch #2's VLANs across to switch #1, so switch #1 sees switch #2's VLAN30 (and vice-versa). Once Switch #1 can "see" VLAN30, I'm assuming I can then apply ACLs as stated in Question #1. Is this correct? Question #3: Once Switch #1 can see all the VLANs, can I achieve the seemingly "Layer 3" ACL filtering of restricting access to Server VLAN on only certain TCP/UDP ports and IP addresses (say, only permitting 3389 to the Terminal Server, 192.168.10.4/32). I say "seemingly" because some of the Layer 2 switches mention the ability to restrict ports and IP addresses through the ACLs; I (perhaps mistakenly) thought that in order to have Layer 3 ACLs (packet filtering), I'd need to have at least one Layer 3 switch acting as a core router. If my assumptions are incorrect, at which point do you need a Layer 3 switch for inter-VLAN routing vs. inter-VLAN switching? Is it generally only when you need that higher-level packet filtering ability between your departments?

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  • how to block spam email using Microsoft Outlook 2011 (Mac)?

    - by tim8691
    I'm using Microsoft Outlook 2011 for Mac and I'm getting so much spam I'm not sure how to control it. In the past, I always applied "Block Sender" and "Mark as Junk" to any spam email messages I received. This doesn't seem to be enough nowadays. Then I've started using Tools Rules to create rules based on subject, but the same spammer keeps changing subject lines, so this isn't working. I've been tracking the IP addresses they also seem to be changing with each email. Is there any key information I can use in the email to apply a rule to successfully place these spam emails in the junk folder? I'm using a "Low" level of junk email protection. The next higher level, "high", says it may eliminate valid emails, so I prefer not to use this option. There's maybe one or two spammers sending me emails, but the volume is very high now. I'm getting a variation of the following facebook email spam: Hi, Here's some activity you have missed. No matter how far away you are from friends and family, we can help you stay connected. Other people have asked to be your friend. Accept this invitation to see your previous friend requests Some variations on the subject line they've used include: Account Info Change Account Sender Mail Pending ticket notification Pending ticket status Support Center Support med center Pending Notification Reminder: Pending Notification How do people address this? Can it be done within Outlook or is it better to get a third party commercial software to plug-in or otherwise manage it? If so, why would the third party be better than Outlook's internal tools (e.g. what does it look for in the incoming email that Outlook doesn't look at)?

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  • how to set up dual wireless routers (G and N) with single broadband connection

    - by user15973
    A local cafe has an 802.11g wireless router attached to either an 8- or 12Mbs broadband connection. Although many customers still have -g devices, an increasing number are showing up with 802.11n devices (e.g. Mac laptops, iPads). The cafe owner is content with his router's area coverage, but he would like for his customers to be able to take advantage of the higher -n download speeds. He could simply replace the -g router with a -n router, but reportedly -n routers slow down considerably when servicing both -g and -n connections. Another option would be to buy the -n router, run an Ethernet cable between the two routers, and (of course) hook up the broadband connection to one of the two routers. Still another option would be to attach an ordinary, wired switch to the broadband connection and then attach both routers to the switch. Aside from the cost issue, what are the tradeoffs of those approaches? Which would you recommend, and why? Is there a better option than the ones I mentioned? Thank you in advance for your advice.

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  • Bad Mumble control channel performance in KVM guest

    - by aef
    I'm running a Mumble server (Murmur) on a Debian Wheezy Beta 4 KVM guest which runs on a Debian Wheezy Beta 4 KVM hypervisor. The guest machines are attached to a bridge device on the hypervisor system through Virtio network interfaces. The Hypervisor is attached to a 100Mbit/s uplink and does IP-routing between the guest machines and the remaining Internet. In this setup we're experiencing a clearly recognizable lag between double-clicking a channel in the client and the channel joining action happening. This happens with a lot of different clients between 1.2.3 and 1.2.4 on Linux and Windows systems. Voice quality and latency seems to be completely unaffected by this. Most of the times the client's information dialog states a 16ms latency for both the voice and control channel. The deviation for the control channels mostly is a lot higher than the one of the voice channels. In some situations the control channel is displayed with a 100ms ping and about 1000 deviation. It seems the TCP performance is a problem here. We had no problems on an earlier setup which was in principle quite like the new one. We used Debian Lenny based Xen hypervisor and a soft-virtualised guest machine instead and an earlier version of the Mumble 1.2.3 series. The current murmurd --version says: 1.2.3-349-g315b5f5-2.1

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  • Keep permalinks in Wordpress

    - by Remus Rigo
    Is there any way to set my permalinks to keep their exact link. If I have a post like this one http://blog.rigo.ro/?p=11, then I would like that every time I edit the post to keep this link. I have installed the Revision Control plugin and I set it to do not keep revisions. Any ideea how to do this? I want to keep this format of links. Edit: I took a look again, the permalinks keep their links, but every time I edit it adds a new version to the database and the next post will have a higher number. If I edit my current post for 3 times (blog.rigo.ro/?p=11) the next post will be blog.rigo.ro/?p=14. Now, my question is how can I keep all my post and edits clean, one post/more edits = one entry in the database, so if I have. 10 post on my site and I edit them, I would like that my permalinks to be from 1 to 10. PS: I don't want to edit my database manually, is there any plugin to do this?

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  • Certificates required for WHQL-certified drivers

    - by Kasius
    The 64-bit Windows 7 image that we deploy to machines at our site does not contain all of the certificates included on a default Windows image. Automatic root certificate installation is also disabled per policy from higher in the organization. We have had a lot of trouble installing many WHQL-certified drivers from reputable companies (ex. HP, Lexmark, Dell, etc.), and I hypothesize that a required certificate is missing from one of the certificate stores on the machine. The error we typically get is: The driver cannot be installed because it is either not digitally signed or not signed in the appropriate manner. I know that it is signed. A .CAT file is included, and it has the following tree from top to bottom: Microsoft Root Authority (thumbprint a4 34 89 15 9a 52 0f 0d 93 d0 32 cc af 37 e7 fe 20 a8 b4 19) Microsoft Windows Hardware Compatibility PCA (thumbprint 93 b8 d8 82 0a 32 db 20 a5 ea b6 8d 86 ad 67 8e fa 14 ea 41) Microsoft Windows Hardware Compatibility Publisher (thumprint b0 50 45 45 42 4e be 2c 16 2f 62 5b bf 5a e6 9b 96 bf 0b 0b) What certificates are required to install WHQL-certified drivers? Is it possibly something other than certificates? Thanks! NOTE: I have posted this question on Technet as well, but honestly, I've never had a lot of luck posting questions on the Technet forums.

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  • Windows VPN for remote site connection drawbacks

    - by Damo
    I'm looking for some thoughts on a particular way of setting up a estate of machines. We have a requirement to install machines into unmanned, remote locations. These machines will auto login and perform tasks controlled from a central server. In order to manage patching, AV, updates etc I want these machines to be joined to a dedicated domain for this estate. Some of the locations will only have 3G connectivity (via other hardware), others will be located on customer premises in internal networks. The central server (of ours) and the Domain Controller will be on a public WAN. I see two ways of facilitating this. Install a router at each location and have a site to site VPN between the remove device and the data centre where the servers are location Have the remote machine dial up and authenticate via a Windows VPN connection to the DC via RAS Option one is more costly to setup and has a higher operational cost. It also offers better diagnostics if the remote PC goes down. Option two works well but is solely dependent on the VPN connection been made before any communication can be made to the remote machine. In a simple test, I can got a Windows 7 machine to dial a VPN prior to authentication to a domain, then automatically login to the machine using domain credentials. If the VPN connection drops, it redials. I can also create a timed task to auto connect every hour in case of other issues. I'd like to know, why (if at all) is operating a remote network of devices which are located in various out of band locations in this way a bad idea? Consider 300-400 remote machines all at different sites. I'd rather have 400 VPN connections to a 2008 server than 400 routers, however I'd like to know other opinions on this.

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  • How far should we take the N+N redundancy craziness ?

    - by Brann
    The industry standard when it comes from redundancy is quite high, to say the least. To illustrate my point, here is my current setup (I'm running a financial service). Each server has a RAID array in case something goes wrong on one hard drive .... and in case something goes wrong on the server, it's mirrored by another spare identical server ... and both server cannot go down at the same time, because I've got redundant power, and redundant network connectivity, etc ... and my hosting center itself has dual electricity connections to two different energy providers, and redundant network connectivity, and redundant toilets in case the two security guards (sorry, four) needs to use it at the same time ... and in case something goes wrong anyway (a nuclear nuke? can't think of anything else), I've got another identical hosting facility in another country with the exact same setup. Cost of reputational damage if down = very high Probability of a hardware failure with my setup : <<1% Probability of a hardware failure with a less paranoiac setup : <<1% ASWELL Probability of a software failure in our application code : 1% (if your software is never down because of bugs, then I suggest you doublecheck your reporting/monitoring system is not down. Even SQLServer - which is arguably developed and tested by clever people with a strong methodology - is sometimes down) In other words, I feel like I could host a cheap laptop in my mother's flat, and the human/software problems would still be my higher risk. Of course, there are other things to take into consideration such as : scalability data security the clients expectations that you meet the industry standard But still, hosting two servers in two different data centers (without extra spare servers, nor doubled network equipment apart from the one provided by my hosting facility) would provide me with the scalability and the physical security I need. I feel like we're reaching a point where redundancy is just a communcation tool. Honestly, what's the difference between a 99.999% uptime and a 99.9999% uptime when you know you'll be down 1% of the time because of software bugs ? How far do you push your redundancy crazyness ?

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  • What performance degradation to expect with Nginx over raw Gunicorn+Gevent?

    - by bouke
    I'm trying to get a very high performing webserver setup for handling long-polling, websockets etc. I have a VM running (Rackspace) with 1GB RAM / 4 cores. I've setup a very simple gunicorn 'hello world' application with (async) gevent workers. In front of gunicorn, I put Nginx with a simple proxy to Gunicorn. Using ab, Gunicorn spits out 7700 requests/sec, where Nginx only does a 5000 request/sec. Is such a performance degradation expected? Hello world: #!/usr/bin/env python def application(environ, start_response): start_response("200 OK", [("Content-type", "text/plain")]) return [ "Hello World!" ] Gunicorn: gunicorn -w8 -k gevent --keep-alive 60 application:application Nginx (stripped): user www-data; worker_processes 4; pid /var/run/nginx.pid; events { worker_connections 768; } http { sendfile on; tcp_nopush on; tcp_nodelay on; keepalive_timeout 65; types_hash_max_size 2048; upstream app_server { server 127.0.0.1:8000 fail_timeout=0; } server { listen 8080 default; keepalive_timeout 5; root /home/app/app/static; location / { proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_set_header Host $http_host; proxy_redirect off; proxy_pass http://app_server; } } } Benchmark: (results: nginx TCP, nginx UNIX, gunicorn) ab -c 32 -n 12000 -k http://localhost:[8000|8080]/ Running gunicorn over a unix socket gives somewhat higher throughput (5500 r/s), but it still does't match raw gunicorn's performance.

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  • Top 5 Reasons to Invest in Enterprise 2.0 Technologies

    - by kellsey.ruppel(at)oracle.com
    In 2010, Oracle's portal, content management, and collaboration solutions evolved rapidly, supported by increasingly deep integrations across Oracle Fusion Middleware and the entire Oracle stack. In light of these developments, we asked Vince Casarez, vice president of Enterprise 2.0 product management, for his top five reasons to invest in Enterprise 2.0 (E2.0) technologies--including real-world examples of businesses already realizing the benefits of next-generation E2.0 technologies. 1. Provide a modern user experience As E2.0 technologies gain widespread adoption, customers and employees expect intuitive Web experiences that are both interactive and community-based. By partnering with Oracle, Alcatel-Lucent Enterprise Group is already making that happen. With 76,000 employees and operations in more than 100 countries, the company wanted a streamlined, personalized user experience with more relevant content in fewer clicks. Working with Oracle, they created a global support portal that supports personalization and integration with Oracle Business Intelligence Enterprise Edition and Oracle E-Business Suite--and drives collaboration with tools such as wikis, blogs, and forums. Learn more about Alcatel-Lucent Enterprise Group's Global Support Portal in this Webcast. 2. Improve productivity and collaboration As E2.0 technologies mature, Oracle anticipates companies moving beyond the idea of simply creating yet another Facebook-like destination for its employees, and instead shaping work environments around specific business tasks. After rapid growth--both organic and through acquisition--construction and infrastructure services leader Balfour Beatty found itself with multiple homegrown intranet sites with very minimal content-sharing capabilities. Today, thanks to Oracle WebCenter Suite, Oracle WebCenter Spaces, Oracle WebCenter Services, and Oracle Universal Content Management, Balfour Beatty is benefiting from collaborative workspaces, a central place to use and work with documents, and unified search across content. 3. Leverage business processes and applications Modern portals are now able to integrate users, content, and business processes in unprecedented ways. To take advantage of these new possibilities, leading dairy provider Land O'Lakes has implemented a fully integrated ERP solution together with Oracle's ECM platform. As a result, Land O'Lakes has been able to achieve better information management and compliance, increased adoption rates for enterprise tools, and increased business process efficiency thanks to more effective information sharing and collaboration. 4. Enhance customer and supplier relationships Companies have begun to move beyond the idea that E2.0 simply means enabling customer reviews or embedding chat functionality. They are taking E2.0 to the next level and providing interactive experiences for their customers. For example, to enhance customer and supplier relationships, Wind River, a global leader in device software optimization, successfully partnered with Oracle to: Integrate ERP and ECM content to provide customers the latest and most relevant support information for products they own Enable customers to personalize their support experience and receive updates regarding patches, application notes, and other relevant content Enable discussions, wikis, and blogs for more efficient collaboration 5. Increase business visibility and responsiveness By strategically embedding collaboration and communication tools into specific business contexts, companies significantly increase visibility into changing business conditions--and can respond much more agilely. Texas A&M University System--one of the largest systems of higher education in the U.S.--partnered with Oracle to create a unified repository that would enable the retrieval of research and grant data from disparate systems via an Enterprise 2.0 user interface. By enabling researchers to customize their own portals with easy-to-use tools, they have also been able to significantly reduce their reliance on the IT department. Learn how other Oracle customers are leveraging Enterprise 2.0 technologies.

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