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• monitoring TCP/IP performance on Solaris

  - by Andy Faibishenko

  I am trying to tune a high message traffic system running on Solaris. The architecture is a large number (600) of clients which connect via TCP to a big Solaris server and then send/receive relatively small messages (.5 to 1K payload) at high rates. The goal is to minimize the latency of each message processed. I suspect that the TCP stack of the server is getting overwhelmed by all the traffic. What are some commands/metrics that I can use to confirm this, and in case this is true, what is the best way to alleviate this bottleneck?

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• How frequent are network partitions on cloud services?

  - by roja

  Much is made of the CAP trade-off for data storage where conflicts can be introduced if there is a network partition. My question is there any evidence that this is a problem that arises with any significant frequency in modern cloud IAAS services e.g.; EC2, Azure, Rackspace. Is it a problem which, despite being a theoretical roadblock in constructing idealised distributed systems is, in fact, a non-issue for all practical concerns? Has anyone experienced a network partition within one of these systems (within a single data-centre?) If so would you be willing to share any details?

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• What should a hosting company do to prepare for IPv6?

  - by Josh

  At the time of writing The IPv4 Depletion Site estimates there are 300 days remaining before all IPv4 addresses have been allocated. I've been following the depletion of IPv4 addresses for some time and realize the "crisis" has been going on for many years and IPv4 addresses have lasted longer than expected, however... As the systems administrator for a small SaaS / website hosting company, what steps should I be taking to prepare for IPv6? We run a handful of CentOS and Ubuntu Linux systems on managed hardware in a remote datacenter. All our servers have IPv6 addresses but they appear to be link local addresses. Our primary business function is website hosting on a proprietary website CMS system. One of my concerns is SSL certificates; at the moment every customer with an SSL certificate gets a dedicated IPv4 IP address. What else should I be concerned about / what action should I take to be prepared for IPv4 depletion?

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• AppFabric named cache, what happens if you lose a cache host?

  - by Liam

  I'm getting my head around how app fabric clustering works and there's something I'm not sure about. Given a structure where we have one named cache, with two lead hosts and (say) three cache hosts and high availability turned off and the lead host(s) performing the management role. When one cache host goes down do you loose the data that was on that cache host? In this MSDN article it states: Data on the non-lead hosts would be lost (assuming high availability was not enabled), but the rest of the cluster could continue serving and storing data But I was unsure if redundancy is built into the system. Would you loose x amount of data or would one of the other cache hosts store this data also and pick up the slack?

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• How is it possible for SSD's drives to have such a good latency?

  - by tigrou

  First time i read some information about SSD's, i was surprised to learn they internally use NAND flash chips. This kind of memory is generally slow (low bandwidth) and have high latency while SSD's are just the opposite. But here is how it works : SSD drives increase their bandwidth by using several NAND flash chips in parallel. In other words, they do some data striping (aka RAID0) across several chips (done by the controller). What i don't understand is how SSD's drives have such a low latency, whereas they are using NAND chips? (or at least lot better than what a typical single NAND chip would do) EDIT: I think under-estimate NAND chip capabilities. USB drives, while powered by NAND's are mostly limited by USB protocol (which have a pretty high latency) and the USB controller. That explain their poor performance in some cases.

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• 8 Character Device names

  - by Lee Harrison

  Is there any reason to still use only 8 characters in a device name? My boss still uses this rule for printers, computers, routers, servers... basicly any device connected to our network. This leads to massive confusion among users, especially when it comes to printer. It also leads to confusion from an administration standpoint because every device is named vaguely, and similarly(its only 8 characters!). I understand the history behind this and compatibility with older systems, but none of our legacy systems will ever make use of PS-printers and Wifi networks. Is there any reason to still do this, and what is everyone else doing when it comes to naming network devices at an enterprise level?

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• Mitigating the 'firesheep' attack at the network layer?

  - by pobk

  What are the sysadmin's thoughts on mitigating the 'firesheep' attack for servers they manage? Firesheep is a new firefox extension that allows anyone who installs it to sidejack session it can discover. It does it's discovery by sniffing packets on the network and looking for session cookies from known sites. It is relatively easy to write plugins for the extension to listen for cookies from additional sites. From a systems/network perspective, we've discussed the possibility of encrypting the whole site, but this introduces additional load on servers and screws with site-indexing, assets and general performance. One option we've investigated is to use our firewalls to do SSL Offload, but as I mentioned earlier, this would require all of the site to be encrypted. What's the general thoughts on protecting against this attack vector? I've asked a similar question on StackOverflow, however, it would be interesting to see what the systems engineers thought.

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• Debian/Ubuntu: Enabling "dist-upgrade" behavior for unattended-upgrades?

  - by Mark Renouf

  We've got a customized distribution of Ubuntu, a repository with some custom packages and we run unattended-upgrades on a number of systems. What we want to be able to do is supply an update of one of our packages which might have a new dependency which is not yet installed. I understand apt normally prevents that from happening automatically, and using dist-upgrade would permit it. How can I get that behavior so our unattended upgrades work the same way? Ideally we'd only want new packages installed if one of our packages causes it to be needed (either as a direct dependency or a child, etc.) Should I be aware of any potential problems or increased risk of breakage. The systems are generally not easily accessed via the console so anything causing a problem requiring manual intervention would be very bad!

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• Distributed website server redundancy

  - by Keith Lion

  Assume a website infrastructure is very complicated and is fully distributed (probably like most large web companies). Am I right in thinking that although there are all these extra web servers to handle multiple client requests, there is still a single "machine" whereby users must enter? I am guessing this machine will be the one physically associated to the IP address? I ask because I need to know whether, in places where distributed systems exist, there is still a single point of failure- usually the control node or, in this example, the machine connected to the public internet? Surely there cannot be two machines connected to the internet, as they would have to have different IP addresses? This "machine" may not be a server per se, but maybe it is a piece of cisco equipment. I just need to know whether, in the real world, these distributed systems still have a particular section where they depend on the integrity of one electronic device?

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• free voice chat over lan

  - by blackjack

  hi is there free a way to voice chat over my lan connected systems without using internet( i use skype for it)?

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• What router hardware or software should be used when multiple public IPs are routed into the same LAN?

  - by lcbrevard

  I am looking for recommendations to replace a set of consumer grade (Linksys, Netgear, Belkin) routers with something that can handle more traffic while routing more than one static public IP into the same LAN address space. We have a block of static public IPs, 5 usable, with Comcast Business. Currently four of them are in use for: General office access Web server Mail and DNS servers Download and backup web server for separate business All systems (a mixture of physical and virtual) are in the same LAN address space (10.x.y.0/24) to enable easy access between them inside the office. There are 30 or more systems in use depending on which virtual machines are currently active. We have a mixture of Windows, Linux, FreeBSD, and Solaris. Currently a separate consumer grade router is used for each of the four static addresses, with its WAN address set to the specific static address and a different gateway address for each: uses 10.x.y.1 - various ports are forwarded to various LAN IPs on systems with gateway 10.x.y.1 uses 10.x.y.254 - port 80 is forwarded to a server with gateway 10.x.y.254 uses 10.x.y.253 - ports for mail and dns are forwarded to a server with gateway 10.x.y.253 uses 10.x.y.252 - ports as needed are forwarded to server with gateway 10.x.y.252 Only router 1. is allowed to serve DHCP and address reservation based on the MAC is used for most of the internal "server" IP addresses so they are at fixed values. [Some are set static due to limitations in the address reservation capabilities of router 1.] And, yes, this really does work! But... I am looking for: better DHCP with more capable address reservation higher capacity so I don't have to periodically power cycle the routers One obvious improvement would be to have a real DHCP server and not use a consumer grade router for that purpose. I am torn between buying a "professional" router such as Cisco or Juniper or Sonic Wall verus learning to configure some spare hardware to perform this function. The price goes up extremely rapidly with capabilities for commercial routers! Worse, some routers require licensing based on the number of clients - a disaster in our environment with so many virtual machines. Sorry for such a long posting but I am getting tired of having to power cycle routers and deal with shifting IP addresses afterwards!

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• Does a hard drive "working hard", i.e. when defragmenting or otherwise continuously active, significantly affect a laptop's temperature?

  - by Marko

  Trying to diagnose and fix an overheating Acer 5735 laptop, running speedfan and doing general workload to try and cause the overheat conditions. I notice that windows xp is badly fragmented according to defraggler, at 58% fragmentation. So I defrag whilst watching the speedfan window, which was at the start reporting high warning style symbols for all of the sensors. After the defrag, I rebooted and ran a few programs, and even defraggler again and the sensors in speedfan all reported green i.e. not high. Wondering if there is a correlation between windows fragmentation causing the hard drive to work harder and produce more heat inside the laptop? dont want to just assume that the problems are resolved, so either speedfan is not accurate enough or fragmentation can lead to additional hard drive heat? All comments or suggestions welcome.

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• Is Protune for video only or may be used for photo too?

  - by Green

  I have Hero3+ Black Edition. I can't understand if Protune is for video only or may be applied for photos? The manual says it is both for video and for photo (page 35): High-Quality Image Capture Protune’s high data rate captures images with less compression, giving content creators higher quality for professional productions. Film/TV Rate Standard While shooting in Protune, you have the option of recording video in cinema quality 24 fps to easily intercut GoPro content with other source media without the need to perform fps conversion. But at the same time their site says that Protune is for video only: To record Protune footage, you’ll need to turn Protune ON in your camera’s settings menu. What for is Protune? Photo? Video? Or both?

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• SSD Performance for PHP?

  - by Andrew Fashion

  My programmer just built an application with PHP using Doctrine ORM (will be a high traffic social networking website), and it's very heavy in PHP/Apache and CPU. The queries are wonderfully fast, and MySQL is barely using any CPU, it's just Apache. I was curious to if an SSD would help speed up PHP/Apache, because I know the bottleneck is in PHP reading multiple files, class files, and loading up a bunch of data. So common sense makes me think if PHP is reading multiple PHP files, an SSD would only help as far as read/write? I was thinking of doing a high performance SSD for the PHP application, but for user image uploads, I would just continue using a 15k SAS. Is there any performance issues regarding using an SSD in this kind of situation? And would it prove to help speed up PHP/Apache, and help the CPU problem out?

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• FPS lags with new acer aspire 5755G

  - by Calvin

  The title is kind of self explanatory, as my new laptop lags and has FPS drops. For example my FPS in Starcraft 2 hovers around 20 and constantly drops to 1 with low settings when I know it should run smoothly in high settings. I've updated my Nvidia driver, and set the preferred global settings to the 'High-performance Nvidia processor'. Here are some screen shots. Screen Shot One - Screen Shot Two - Screen Shot Three I'm not sure how to fix this problem, any feed back would be nice!

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• When should I upgrade to Ubuntu 10.04 (Lucid Lynx)? [closed]

  - by Emyr

  I'm a web developer for a small non-IT firm. When 9.10 came out, I was using it with no adverse effects from about a month before release (iirc, first beta), initially as an upgrade but as a clean install later to ensure my system would be consistent with most other 9.10 systems. The last alpha of 10.04 came out last week, with another 2 weeks before beta. I'm quite eager to do it today, but obviously the usual "not for production systems" notice is still in place. When should I upgrade? Do I need to worry about software installed from source? (./configure, make, make install etc) Is the attraction of a non-brown theme really this tempting for you?

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• SSH and Latent Connections (e.g., satellite connections)

  - by user71494

  Most of the week I live in the city where I have a typical broadband connection, but most weekends I'm out of town and only have access to a satellite connection. Trying to work over SSH on a satellite connection, while possible, is hardly desirable due to the high latency ( 1 second). My question is this: Is there any software that will do something like buffering keystrokes on my local machine before they're sent over SSH to help make the lag on individual keystrokes a little bit more transparent? Essentially I'm looking for something that would reduce the effects of the high latency for everything except for commands (e.g., opening files, changing to a new directory, etc.). I've already discovered that vim can open remote files locally and rewrite them remotely, but, while this is a huge help, it is not quite what I'm looking for since it only works when editing files, and requires opening a connection every time a read/write occurs. (For anyone who may not know how to do this and is curious, just use this command: 'vim scp://host/file/path/here)

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• Is there a way to get a 10000x10000 virtual resolution desktop?

  - by pingo

  I have a java applet map viewer and I'd like to plot out the map it displays. To do that I need to open it in a high enough resolution to avoid too much stitching. Is there any possible way I could get a desktop with such high resolution? So far I've been able to use panning 2560x1920 by booting windows 7 in VmWare Player. Would it be possible to get it higher? Maybe this would be doable on Linux? The whole thing can be laggy as hell as long as it will render my screenshot...

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• Apache stops serving requests when connections increase

  - by Gunjan

  The values for MaxClients, ServerLimit etc parameters are quite high (4000). Available RAM on the server is high too (~8G). Load average remains below 1 on a 24 core CPU. But when the number of visitors on the website increase apache just stops serving requests. The apache error log is blank and access log shows no more requests coming in. Restarting apache makes it work again until the number of requests increases again. Any ideas where to start looking? UPDATE Getting the below errors in apache error log on running it with LogLevel Debug [info] server seems busy, (you may need to increase StartServers, or Min/MaxSpareServers), spawning 32 children, there are 479 idle, and 1027 total children

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• Is there a filesystem that is "friendly" to both windows and Linux?

  - by Somebody still uses you MS-DOS

  I'm planning to install Ubuntu 10.04 with Windows 7. (I'm new to Linux, have to use at work so I'm planning to install it at home to learn more) I plan to use a partition to my Windows system files (C:), a partition for my personal files that already exists (D:) and a new partition for Linux. What I want is to have a partition for my personal files that works across these systems - so, if I start with Windows or Linux, there's the same "Videos", "Pictures", "Projects" folders. Is it possible? Is there a hd filesystem capable of having writes from both systems without too much risk of corrupting or something?

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• Is there a filesystem that is "friendly" to both windows and Linux?

  - by Somebody still uses you MS-DOS

  I'm planning to install Ubuntu 10.04 with Windows 7. (I'm new to Linux, have to use at work so I'm planning to install it at home to learn more) I plan to use a partition to my Windows system files (C:), a partition for my personal files that already exists (D:) and a new partition for Linux. What I want is to have a partition for my personal files that works across these systems - so, if I start with Windows or Linux, there's the same "Videos", "Pictures", "Projects" folders. Is it possible? Is there a hd filesystem capable of having writes from both systems without too much risk of corrupting or something? (Can't be FAT32, I need to store 4gb files). I've read some horror stories of corruption, and would like to know from a sysadmin POV all the risks involved in such scenario.

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• Straight-forward to Virtualise with XEN or KVM on IBM Server System x3650 M4 791562G?

  - by ChrisZZ

  I want to built a virtualised Server Environment using XEN or KVM. The virtual machines should be purely debian systems - so XEN or KVM should be a sane choice. Now while buying servers, I am confronted with the fact, that the vendors obviously only support commercial solution. I think, on a good server, one should be able to install uncommercial software as well - but of course sometimes systems have hardware, that requires drivers, that are not found in the OS Community. So I am asked the question: Is it straight-forward to use Debian with IBM Server System x3650 M4 791562G with Debian - or even virtualising the IBM Server System x3650 M4 791562G using XEN or KVM. I am sure there will always be a way to achieve this goal - but this way might have a high milage - so I am not asking, whether this is theoretical possible, but whether this should be straight-forward and practically easy to do, no major headaches to be expected.

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• Server Overload Due To Log File

  - by emresavas

  cPanel sent me the following email: IMPORTANT: Do not ignore this email. This is cPanel stats runner on ***.***.com! While processing the log files for user ***, the cpu has been maxed out for more than a 6 hour period. The current load/uptime line on the server at the time of this email is 04:41:14 up 15 days, 22:36, 0 users, load average: 7.66, 7.84, 8.00 You should check the server to see why the load is so high and take steps to lower the load. If you want stats to continue to run even with a high load; Edit /var/cpanel/cpanel.config and change extracpus to a number larger then 0 (run /usr/local/cpanel/startup afterwards to pickup the changes). How can I lower the load?

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• Can an ESX server under heavy load cause cpu spikes on guest VM's?

  - by ReferentiallySeethru

  So we have a number of vm's running on an ESX 4.1 server for product testing. The ESX Server is at times under heavy load. We've been experiencing high CPU levels during some use cases, but we can't always duplicate this. If the ESX server as a whole is under heavy load could this cause guest machines to show high CPU usage? To ask it a different way, if the guest machines require more cpu resources than the server has, how does this affect CPU usage as indicated by the OS and process?

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• Conficker keeps coming back

  - by PHLiGHT

  I hadn't run into anyone who actually got this virus until recently when dealing with a new client that didn't believe in patching their systems and consquently have been hit with this pest. I was under the impression that if you have KB958644 installed and ran the latest malicious software removal tool that conficker would be squashed. I have several systems that are fully patched, MSRT has removed the virus yet the bugger keeps coming back. This has even happened to a file server and a Domain Controller. What am I missing here? They are running AVG which I used to recommend but I have been doubting it's effectiveness over the past year or so.

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