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• What hardware would I need (approx) to run ESXi server?

  - by mr.b

  Hi, I am considering to purchase off-the-shelf commodity hardware in order to build server that will host virtual machines using ESXi server. Intended purpose for this server is NOT mission critical tasks. It will have to run perhaps 20-50 Windows XP/Vista/7 virtual machines (in total, but closer to 20 figure). Each guest would have to have 1-2 GB of ram, and probably two-three times more disk space than guest OS needs with clean install and all updates applied (that would be around 6-8 GB for XP, and i believe closer to 10-15 for win7). Those guests will act as a test ground for a new product that is network management software, thus guests will idle most of their time once initially loaded, but if I give them some task to complete, they should be able to perform reasonably well. Now, from what I have learned... CPU is usually not much of an issue (6 cores would do it), memory should not be lacking, but doesn't have to be sum of all guests, because of overcommitment... That leads me to IO, which is, as it seems, the bottleneck. Since I have very little experience with ESXi (and ESX, too) server, I'd like to ask: How much memory could I save by overcommitment, and how does it affect performance? Is 6-core cpu enough to run above described system? Would it be possible to run entire server off two (or even one) SSD drives (to host system virtual disks, with few additional HDDs (2-3) in RAID 0 to be used as secondary storage? I read somewhere that ESXi allows having something like "master image", essentially virtual machine that is "deployed" many times, so that disk space can be saved by having only differences stored by specific guests, instead of copying around whole virtual disks. Is this true, and how can this help me? Are there any other things I need to take into consideration when building this off-the-shelf solution? I should probably mention here that I'm fully aware of issues like SPOF regarding power supply, raid 0, etc, but since it's only a testing ground and not a production system, it's not so important for me. Thanks, B.

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• Master File Table Corrupt, any way to save data?

  - by domen

  hi. I've used search, but none of the results match my problem so I didn't have to ask separate question. I've Installed Windows 7 RTM recently and since then partitions located on one of my HDDs have gone "crazy". They used to "freeze" and didn't open in explorer for some time (minute or two, usually), sometimes all partitions of the drive wouldn't show until reboot and finally, one of those partitions started showing "disk structure is corrupted and unreadable" warning, it appeared in Disk Management window as RAW and chkdsk showed "mft corrupt". There were no important data on the partition and I didn't have enough time to analyze the problem at the moment, so I just reformatted it and ran antivirus scan on system. After that problem settled for some time, but yesterday the problematic HDD vanished again from the system. After reboot chkdsk identified mft of four partitions corrupt and now they are all in same conditions as the above mentioned one. But the difference is that the files stored in them are extremely important. and just for info: I upgraded from Win7 build 7077, but had some performance issues, so I reformatted system drive and installed fresh Win7 RTM on it. I've downloaded TestDisk and it shows all the partitions marked as NTFS (not RAW) and my knowledge of the program wasn't sufficient to obtain any other info from it :-) and the images that could help describe the problem (sorry, I'm not allowed to post images and more than one hyperlink): http:// img22.imageshack.us/img22/5909/chkdskz.jpg http:// img198.imageshack.us/img198/5576/computeray.jpg I'm interested, is there a way to let me restore the MFT or just access files so I can backup them before reformatting the drive. Thanks for your time. :) P.S. my reformatted drive is showing no problems, could there be a problem with windows 7 itself? I googled, but with no results.

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• Tuning Linux + HAProxy

  - by react

  I'm currently rolling out HAProxy on Centos 6 which will send requests to some Apache HTTPD servers and I'm having issues with performance. I've spent the last couple of days googling and still can't seem to get past 10k/sec connections consistently when benchmarking (sometimes I do get 30k/sec though). I've pinned the IRQ's of the TX/RX queues for both the internal and external NICS to separate CPU cores and made sure HAProxy is pinned to it's own core. I've also made the following adjustments to sysctl.conf: # Max open file descriptors fs.file-max = 331287 # TCP Tuning net.ipv4.tcp_tw_reuse = 1 net.ipv4.ip_local_port_range = 1024 65023 net.ipv4.tcp_max_syn_backlog = 10240 net.ipv4.tcp_max_tw_buckets = 400000 net.ipv4.tcp_max_orphans = 60000 net.ipv4.tcp_synack_retries = 3 net.core.somaxconn = 40000 net.ipv4.tcp_rmem = 4096 8192 16384 net.ipv4.tcp_wmem = 4096 8192 16384 net.ipv4.tcp_mem = 65536 98304 131072 net.core.netdev_max_backlog = 40000 net.ipv4.tcp_tw_reuse = 1 If I use AB to hit the a webserver directly I easily get 30k/s connections. If I stop the webservers and use AB to hit HAProxy then I get 30k/s connections but obviously it's useless. I've also disabled iptables for now since I read that nf_conntrack can slow everything down, no change. I've also disabled the irqbalance service. The fact that I can hit each individual device with 30k/s makes me believe the tuning of the servers is OK and that it must be some HAProxy config? Here's the config which I've built from reading tuning articles, etc http://pastebin.com/zsCyAtgU The server is a dual Xeon CPU E5-2620 (6 cores) with 32GB of RAM. Running Centos 6.2 x64. The private and public interfaces are on separate NICS. Anyone have any ideas? Thanks.

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• Recommendations for good Unix MTA / groupware solutions? [closed]

  - by Jez

  Possible Duplicate: Exchange server replacement that runs on Linux I'm setting up a Debian server, and one of the things I need on it is an MTA. I don't want to use something like Exim or Postfix because I want something that ties in SMTP, POP3, and IMAP all in one (a la Microsoft Exchange). Most MTAs also seem to be hellishly difficult to configure. Try and read the Exim documentation; you could do a university degree on it (I'm not kidding). When you can get an HTTP server like Cherokee which is easy to configure and has a nice web interface, do MTAs or groupware solutions need to be that hard? I'm aware that some people think "the Unix way" is to have lots of different interacting pieces of software (like maybe an SMTP MTA, POP3 service, webmail service, and overarching manager to tie them all together), but I think this is a situation where that just makes things a lot harder to deal with and one large software suite fits in much more nicely. So, I'm looking for good open source software suites that will run on Debian that: Combine (at least) SMTP, POP3, and IMAP Are easy(ish) to configure Have a nice configuration web interface or GUI Are not defunct projects I don't mind if it's groupware and offers calendaring too, but I would only be using the e-mail functionality for now. Another nice-to-have would be built-in webmail (if we're combining a bunch of functionality, why not?) Note however that I do NOT need Outlook support. I am not really looking for an "Exchange replacement drop-in". The suites I've found so far that seem to match the above criteria (and have appropriate licenses) are Citadel, Kolab, and Zimbra. I'd appreciate anyone who has experience with any of these giving me the pros and cons of them, such as how easy they are to configure and what their performance is like. I'd also appreciate any other suggestions for solutions that fulfil my criteria that I may have missed out.

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• ASP.Net Session Timing Out Rapidly

  - by Zac

  We have an ASP.Net 3.5 website running on Windows Server 2008 with IIS7. The session timeout period for this site is configured to be 20 minutes - however, it is currently lasting for between 40 and 50 seconds. After researching the problem we investigated several configuration values which could be involved in the timeout period but none of them are set to less than 20 minutes. The areas we look are as follows: web.config system.web/sessionState element (20 minutes). web.config system.web/authentication/forms element (not present, defaults to 30 minutes). Sites/{website}/ASP/Session Properties/Time-out (20 minutes). Application Pools/{appPool}/Advanced Settings/Process Model/Idle Time-out (20 minutes). We've also noted that the CPU is staying around 0% and that RAM usage is flat-lining around 1.07 GB (of 8 GB available) - so there is no performance-based reason for IIS to be recycling the Application Pool as far as we can tell. Are there any settings we've overlooked which could cause the session timeouts to be expiring so quickly? EDIT A couple of additional points: This is not occurring in development, only on the server. The session is not sliding (i.e. if we refresh the page a few times it still times out approximately 40 - 50 seconds after the session was created.

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• 150 TB and growing, but how to grow?

  - by seandavi

  My group currently has two largish storage servers, both NAS running debian linux. The first is an all-in-one 24-disk (SATA) server that is several years old. We have two hardware RAIDS set up on it with LVM over those. The second server is 64 disks divided over 4 enclosures, each a hardware RAID 6, connected via external SAS. We use XFS with LVM over that to create 100TB useable storage. All of this works pretty well, but we are outgrowing these systems. Having build two such servers and still growing, we want to build something that allows us more flexibility in terms of future growth, backup options, that behaves better under disk failure (checking the larger filesystem can take a day or more), and can stand up in a heavily concurrent environment (think small computer cluster). We do not have system administration support, so we administer all of this ourselves (we are a genomics lab). So, what we seek is a relatively low-cost, acceptable performance storage solution that will allow future growth and flexible configuration (think ZFS with different pools having different operating characteristics). We are probably outside the realm of a single NAS. We have been thinking about a combination of ZFS (on openindiana, for example) or btrfs per server with glusterfs running on top of that if we do it ourselves. What we are weighing that against is simply biting the bullet and investing in Isilon or 3Par storage solutions. Any suggestions or experiences are appreciated.

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• SQL Server 2005 SE SP3 on Windows Server 2008 R2 x64 premature query disconnections

  - by southernpost

  New Dell PowerEdge R910, 4x8 Intel X7560, 192GB RAM, hardware NUMA, local RAID, Broadcom NetExtreme II multiport NIC, unteamed, TCP Offload disabled, RSS disabled, NetDMA disabled, Hyperthreading disabled. SQL Server 2005 SE x64 SP3 on Windows Server 2008 R2 EE x64. No other apps on server. Max Mem = 180GB, Max DOP = 4. Existing Windows Server 2003 R2 EE x64 app server connecting to Dell via firewall using SQL Authenticated logins. Symptoms: Intermittent errors at the app server: A transport-level error has occurred when sending the request to the server. (provider: TCP Provider, error: 0 - An existing connection was forcibly closed by the remote host.) Findings: Running queries from SSMS located on another machine within the same domain as the SQL Server run without error. SQLIO showed good performance. Windows and SQL logs show no related messages. Microsoft reveiwed PssDiag trace and stated that "We are not seeing timeouts from SQL Side. The queries bring run against the database are timing out within 9secs. This is a database connectivity error." "we can also see from the AttnSeq column that we are also not seeing any Attentions from the SQL Side.". Dell has confirmed that we are using the latest Broadcom drivers.

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• Hyper-V and attaching physical disks

  - by Mike Christiansen

  So, I'm looking at rebuilding my home server. My current setup is the following Windows 7 Ultimate 1TB Boot Drive (my smallest drive) Windows Dynamic Spanned volume, continaing 1x 1TB drive, 2x 2TB drives, totalling 5TB. I am upgrading to a hardware RAID controller, and I would like to run Hyper-V server core. However, I want to retain the ability to join my "file server" to a homegroup, so I must use Windows 7. I know VHDs can only be like 127GB or something, so I obviously need to directly connect disks to my Windows 7 machine. Here is my plan: Server Core 2008 R2 (Hyper-V) 1TB Boot Drive (storing VHDs for boot drives of VMs) - possibly in a RAID 1 with my other 1TB drive 5x 2TB drives (1x 2TB drive hot spare), totalling 10TB, directly attached to a Windows 7 VM, for use of homegroup for this array. In the past, I directly attached the windows dynamic volume to a Windows 7 VM, and performance was abysmal. The question is, with hardware RAID, will it really make that much of a difference? Server specs: Intel Core 2 Quad Q9550 2.83GHz Asus Maximus II Formula (PCI-E x16) 8GB DDR2 RAM PC2-6400 (Yes, I know its a bit out of date)

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• Windows 7 x64 support for Intel GMA 3650 (or GMA 3600)

  - by Loom

  I recently purchased an Intel D2700 MUD motherboard and I cannot find drivers for the Win7 x64 integrated graphics (Intel GMA 3650 aka PowerVR sgs545). The accompanying CD contains Win7 x32 version only. When I run it I got an error: This computer does not meet the minimum requirements for installing the software. I tried to use online utility Intel Driver Update Utility Graphics. I used Chrome, Firefox, Internet Explorer without success. First, UAC prompt appear, and then endlessly spinning progress-bar with text "Analyzing computer...". The text in UAC prompt is: Program file name: System Requirements Lab Verified publisher: Husdawg, LLC I downloaded this utility (intel_srldetect_4.5.5.0) and started it from my hard disk. I got an error: A network error occured while attempting to read from the file: C:\Users\Loom\Downloads\SystemRequirementsLab_intel_4.5.5.0.msi Standard VGA driver works for this video card but without hardware acceleration: Hardware acceleration is either disabled or not supported by your video card driver, which could slow game performance. Make sure you have the latest video card driver installed and that hardware acceleration is turned on. Where I can get appropriate driver?

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• All applications quit when printing on Mac OS X 10.5.8

  - by Tamany

  I recently ran a software update. I'm not sure if my problems are associated with this but I'm pretty sure they are as I printed successfully before update. I checked the log at time of printing: 03/05/2010 22:03:15 Microsoft Word[697] *** -[NSCFString _getValue:forType:]: unrecognized selector sent to instance 0x17a82b50 03/05/2010 22:03:15 [0x0-0x51051].com.microsoft.Word[697] Ignoring Quickdraw drawing between QDBeginCGContext and QDEndCGContext 03/05/2010 22:03:16 [0x0-0x51051].com.microsoft.Word[697] Ignoring Quickdraw drawing between QDBeginCGContext and QDEndCGContext 03/05/2010 22:03:16 [0x0-0x51051].com.microsoft.Word[697] Ignoring Quickdraw drawing between QDBeginCGContext and QDEndCGContext 03/05/2010 22:03:16 [0x0-0x51051].com.microsoft.Word[697] Ignoring Quickdraw drawing between QDBeginCGContext and QDEndCGContext 03/05/2010 22:03:16 [0x0-0x51051].com.microsoft.Word[697] Ignoring Quickdraw drawing between QDBeginCGContext and QDEndCGContext 03/05/2010 22:03:16 [0x0-0x51051].com.microsoft.Word[697] Ignoring Quickdraw drawing between QDBeginCGContext and QDEndCGContext 03/05/2010 22:03:17 [0x0-0x51051].com.microsoft.Word[697] Mon May 3 22:03:17 leopards-imac-2.local Word[697] <Error>: The function `CGPDFDocumentGetMediaBox' is obsolete and will be removed in an upcoming update. Unfortunately, this application, or a library it uses, is using this obsolete function, and is thereby contributing to an overall degradation of system performance. Please use `CGPDFPageGetBoxRect' instead. 03/05/2010 22:22:09 Microsoft Word[697] *** -[NSCFString _getValue:forType:]: unrecognized selector sent to instance 0x1b036500 Any thoughts on how to fix this?

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• Mod_pagespeed, Varnish and Apache cache issues after new code pushes

  - by WerkkreW

  I have a rather strange issue. In my environment we are running a load balanced cluster of 8 apache servers with a master-master MySQL backend. In front of apache we have Varnish in the cache layer. We have been running Apache mod_pagespeed for several weeks now and for the most part it has been working great. The issue arises when we do fresh code updates from Git, and and/all of the JS/CSS assets change. Basically the problem appears to be two fold. One, after the code push we generally take the opportunity to flush varnish, restart apache, and restart varnish. In doing this all of the mod_pagespeed combinied/minified files are cleared out ensuring that all of the new JS/CSS assets are fresh. The problem is, upon doing this the file names that mod_pagespeed creates change, but the old files (appear) to be still cached for many people client side leading to very unexpected results. However, if we do not restart apache, the changes to the files may or may not appear client side due to the cached minified assets. The simple solution is to disable mod_pagespeed, however I would rather not do that as it has made a fairly large impact in performance. I feel as if there must be a better way to deal with the inconsistencies in cache between the client and server to prevent having people to go to great lengths or perform a large number of page refreshes to see a working page. I can provide configuration snippets if anyone needs them. If you would like to inspect the site, source, headers, or anything try the following addresses: http://wellplayed.org http://wellplayed.org/tv Thanks in advance!

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• Suggestions for Backup solution

  - by jiewmeng

  i am considering between windows home server simple nas extra HDD's in desktop btw, i will be the main user i am looking to fulfil the following needs: reliability (i am think RAID 1 or 5) not so prone to virus/malware infections (will using a separate NAS or home server help? say windows home server is still a windows pc except separated by network?) power efficiency (eg. spin down when not in use) download (eg. i may want to dl big files/torrents overnight and i may not want to use a full powered PC for it? does a full pc vs NAS provide significant power usage to justify cost of new system esp. since i am only user?) performance (i guess i like to write/access my files fast, on 2nd thought, maybe for backup i can forgo this? maybe for a WD Green HDD? but how much slower will it be? plus since i am the only user, i think the whole HDD will be mine?)

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• How do I speed up and cache mmap file access over NFS on Linux?

  - by Zan Lynx

  The server and client are both 64-bit Ubuntu 10.04 LTS. The application in question is a custom app that uses mmap() for fast random file access. Its ideal state is when the entire file is cached in RAM. The network connections are really fast 10Gb Ethernet. It is a virtual server blade setup. It isn't the network connections slowing things down because everything performs superbly when using a virtual disk (iSCSI to the SAN). But when we run the application on a NFS home directory mount, performance goes to the dogs. It appears that the Linux kernel isn't caching anything. So it is reading every single disk block needed by mmap() accesses over and over and over again. The NFS mount is done through autofs, which has only default settings. /proc/mounts shows the NFS mount is done with the following options: rw,relatime,vers=3,rsize=131072,wsize=131072,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=192.168.11.52,mountvers=3,mountproto=tcp,addr=192.168.11.52 How can I make Ubuntu 10.04 cache the file instead of reloading it all the time?

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• Installed Bunch of New Fonts on Windows 7 - Now None Show Up and System Lags

  - by Josh Stodola

  So I went to install about 5,000 fonts on my Windows 7 64-bit machine. It was slow to install them, and I had to leave. I came back and my PC was shut down, and I had to go through the Windows recovery BS when I powered it on. Now my computer runs EXTREMELY slow and any program that has a font menu locks up my whole machine (nothing in Microsoft Office works). When I go to "Fonts" in the control panel, it says 0 items. I went through all of the font settings trying to get them to appear. Nothing helps. I tried to bring up the Character Map and that froze up my machine too. How can I fix this? If I do not get this issue resolved soon, I am wiping this drive and going back to XP (and probably never purchasing another version of Windows again). I never had any issues with XP and have had nothing but performance problems when switching to Windows 7. My quad-core intel extreme with 8GB of RAM should never flinch with the kind of work that I do, and something simple like playing a song off an external HD takes up to five seconds on Windows 7. Unbelievable that I had to pay for this crap!

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• windows: force user to use specific network adapter

  - by Chad

  I'm looking for a configuration/hack to force a particular application or all traffic from a particular user to use a specific NIC. I have an legacy client/server app that has a "security feature" that limits connections based on IP address. I'm trying to find a way to migrate this app to a terminal server environment. The simple solution is for the development team to update the code in the application, however in this case that's not an option. I was thinking I might be able to install VMware NIC's installed for each user on the terminal server and do some type of scripting to force that user account to use a specific NIC. Anybody have any ideas on this? EDIT 1: I think I have a hack to work around my specific problem, however I'd love to hear of a more elegant solution. I got lucky in that the software reads the server IP address out of a config file. So I'm going to have to make a config file for each user and make a customer programs files for each user. Then add a VMware NIC for each user and make each server IP address reside on a different subnet. That will force the traffic for a particular user to a particular IP address, however its really messy and all the VM NIC's will slow down the terminal server. I'll setup a proof of concept Monday and let the group know how it affects performance.

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• Why does my simple Raid 1 backup storage perform really slow sometimes?

  - by randomguy

  I bought 2x Samsung F3 EcoGreen 2TB hard disks to make a backup storage. I put them in Raid 1 (mirror) mode. Made a single partition and formatted it to NTFS, running Windows 7. For some reason, accessing the drive's contents (simply by navigating folders) is sometimes really slow. Like opening D:/photos/ can sometimes take several seconds before it starts showing any of the folder's contents. Same applies for other folders. What could be causing this and what could I do to improve the performance? I remember that there was an option somewhere inside Windows to choose fast access but less reliable persistence operations (read/write). It was a tick inside some dialog. At the time, it felt like a good idea to take the tick away from the option and get more reliable persistence but slower access, but now I'm regretting. I'm unable to find this dialog.. I've looked hard. I don't know, if it would make any difference. Oh, and I've ran scan disk and defrag on the drive. No errors and speed isn't improved.

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• Computer making strange sound when turned on, ever since power outage

  - by Dot NET

  Recently we experienced a power outage, and the PC was off. However, once the power came back, I switched on the PC and heard a strange noise - almost as if the hard disk or fans were struggling to work. I can't really describe the sound, but it's a laboured, loud sound almost like a jack-hammer. This has been persisting ever since the power outage, however the noise stops after around 10 minutes or so, and doesn't start again until the computer is turned off and on again. At first I thought it had something to do with the HDD, but all my files are intact, chkdsk did not report any issues and performance is 100% unchanged, even in games (so the gfx card is fine, and so is the HDD most likely). My PC setup basically has around 3 cooling fans, but I'm not sure if it's one of these either as the noise actually stops after 10 minutes or so, and if I leave the PC on for 4 hours (for example) the noise never starts again. It's there solely when turning on the PC. I haven't got a UPS, and it's important to note that the computer was not on when the power went out - it was merely plugged in. I then promptly unplugged the PC once the power was out, and only plugged it in again when the power came back. Could it be the power supply? Unfortunately I can't open my tower as I would void the warranty. Are there any tests which I could carry out without voiding the warranty?

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• 3dmark score abnormal

  - by Sean

  I just bought a new laptop. It is core i7 3610QM.(Ivy bridge, 4 core plus hyperthreading), 8G ram, nvidia GT 610M 2GB. The OS is Win7 64bit. I ran 3dmark 11, but the score is frustrating. For 1280*720, the score is P730. It is too low right? I searched online, the score should at least above 1000. Am I right? I never use this software before. I know nvidia has optimus, so I made the laptop in high performance state and white-listed the 3dmark program. But there is no help. I am guessing 3dmark is using i7's graphic module. It cannot transform to nvidia. In the running detail of 3dmark, the graphic card cannot be identified(The row remain blank). Can anybody tell me is this the normal case? If not, can I use some other software to test if my nvidia card is working fine? If this nvidia card cannot work, I will return the new laptop asap. Thanks.

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• Bypass network stack. Which options do we have? Pros and cons of each option [on hold]

  - by javapowered

  I'm writing trading application. I want to bypass network stack in Linux but I don't know how this can be done. I'm looking for complete list of options with pros and cons of each of them. The only option I know - is to buy solarflare network card which supports OpenOnLoad. What other options should I consider and what is pros and cons of each of them? Well the question is pretty simple - what is the best way to bypass network stack? upd: OpenOnload It achieves performance improvements in part by performing network processing at user-level, bypassing the OS kernel entirely on the data path. Intel DDIO to allow Intel® Ethernet Controllers and adapters to talk directly with the processor cache of the Intel® Xeon® processor E5. What's key difference between these techologies? Do they do roughly the same things? I much better like Intel DDIO because it's much easy to use, but OpenOnload required a lot of installation and tuning. If good OpenOnload application is much faster than good Intel DDIO application?

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• Ram configuration 4x4 or 2x8?

  - by Carl B

  I am looking to upgrade my Ram to 16gigs and I am wondering if there is any distinct advantage of the way I do it. That being a 4x4 or 2x8 set up. In all my searching there have been a number of pros for each profile. I can find no benchmarck results for either setup as a compaison. So, if there are 2 profiles of the same speed, same voltage, same timing and same cas what would perform better or have a better over all benafit? A few examples from my search - a 4x4 set would lend a benafit in that if one stick failed, you only lose 25% of your Ram vs 50% in a 2x8 set up. a 2x8 set up would have less strain on the memory controler and motherboard. a 2x8 would generate less heat. a 2x8 set up is easier to over clock (not part of my need, but alot of the comparisons circled around the overclocability ease of the 2 stick set up). There is one outstanding benafit that I have found in at least the target company I have looked at and that is price. The 2x8 is nearly half the cost. My motherboard supports a max of 16 gigs and I have a 64 bit OS. Has anyone seen any performance comparisons or is 16 gb just 16 gb no matter how you slice it? And is there any merit to the above pros? Edit: as per the mobo specs - Main Memory • Supports four unbuffered DIMM of 1.5 Volt DDR3 800/1066/1333/1600*/1800*/2133* (OC) DRAM, 16GB Max

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• pam_ldap.so before pam_unix.so? Is it ever possible?

  - by user1075993

  we have a couple of servers with PAM+LDAP. The configuration is standard (see http://arthurdejong.org/nss-pam-ldapd/setup or http://wiki.debian.org/LDAP/PAM). For example, /etc/pam.d/common-auth contains: auth sufficient pam_unix.so nullok_secure auth requisite pam_succeed_if.so uid >= 1000 quiet auth sufficient pam_ldap.so use_first_pass auth requiered pam_deny.so And, of course, it works for both ldap and local users. But every login goes first to pam_unix.so, fails, and only then tries pam_ldap.so successfully. As a result, we have a well-known failure message for every single ldap user login: pam_unix(<some_service>:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=<some_host> user=<some_user> I have up to 60000 of such log messages per day and I want to change the configuration so, that PAM will try ldap authentication first, and only if it fails - try pam_unix.so (I think it can improve the i/o performance of the server). But if I change common-auth to the following: auth sufficient pam_ldap.so use_first_pass auth sufficient pam_unix.so nullok_secure auth requiered pam_deny.so Then I simply can't login anymore with local (non-ldap) user (e.g., via ssh). Does somebody knows the right configuration? Why Debian and nss-pam-ldapd have pam_unix.so at first by default? Is there really no way to change it? Thank you in advance. P.S. I don't want to disable logs, but want to set ldap authentication on the first place.

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• Anyone have real world experience with Rackspace Cloud Sites at high scale?

  - by Allara

  I have a pure web service application layer using .NET. I was originally planning to use Amazon EC2, but rolling my own autoscaling procedures is a bit intimidating, and the scaling isn't very granular from a cost perspective. If the app is successful, we could be looking at relatively high scale (millions of requests per month). The app uses Amazon SimpleDB as the database layer. As a test, I have the app running successfully in Rackspace Cloud Sites. Performance seems to be equal to (if not better than) a standard EC2 instance, even with the added latency of the SimpleDB requests travelling to the Rackspace network. However, testing at this stage is at a very low scale. My question is this: has anyone had real-world experience running a high scale application on Rackspace Cloud Sites? Moreover, once you pass the "included" 10,000 compute cycles per month, does the overall cost seem to be lower than rolling lots of EC2 instances? My assumption would be that with completely smooth scaling (i.e. only adding compute resources as needed), the cost could be lower on average. However, their stated goal of calibrating 10,000 CCs as a single 1.2 Ghz CPU seems on average to be much more expensive than EC2. I like the idea of no-touch scaling, but is it too good to be true?

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• Tuning up a MySQL server

  - by NinjaCat

  I inherited a mysql server, and so I've started with running the MySQLTuner.pl script. I am not a MySQL expert but I can see that there is definitely a mess here. I'm not looking to go after every single thing that needs fixing and tuning, but I do want to grab the major, low hanging fruit. Total Memory on the system is: 512MB. Yes, I know it's low, but it's what we have for the time being. Here's what the script had to say: General recommendations: Run OPTIMIZE TABLE to defragment tables for better performance MySQL started within last 24 hours - recommendations may be inaccurate Enable the slow query log to troubleshoot bad queries When making adjustments, make tmp_table_size/max_heap_table_size equal Reduce your SELECT DISTINCT queries without LIMIT clauses Increase table_cache gradually to avoid file descriptor limits Your applications are not closing MySQL connections properly Variables to adjust: query_cache_limit (> 1M, or use smaller result sets) tmp_table_size (> 16M) max_heap_table_size (> 16M) table_cache (> 64) innodb_buffer_pool_size (>= 326M) For the variables that it recommends that I adjust, I don't even see most of them in the mysql.cnf file. [client] port = 3306 socket = /var/run/mysqld/mysqld.sock [mysqld_safe] socket = /var/run/mysqld/mysqld.sock nice = 0 [mysqld] innodb_buffer_pool_size = 220M innodb_flush_log_at_trx_commit = 2 innodb_file_per_table = 1 innodb_thread_concurrency = 32 skip-locking big-tables max_connections = 50 innodb_lock_wait_timeout = 600 slave_transaction_retries = 10 innodb_table_locks = 0 innodb_additional_mem_pool_size = 20M user = mysql socket = /var/run/mysqld/mysqld.sock port = 3306 basedir = /usr datadir = /var/lib/mysql tmpdir = /tmp skip-external-locking bind-address = localhost key_buffer = 16M max_allowed_packet = 16M thread_stack = 192K thread_cache_size = 4 myisam-recover = BACKUP query_cache_limit = 1M query_cache_size = 16M log_error = /var/log/mysql/error.log expire_logs_days = 10 max_binlog_size = 100M skip-locking innodb_file_per_table = 1 big-tables [mysqldump] quick quote-names max_allowed_packet = 16M [mysql] [isamchk] key_buffer = 16M !includedir /etc/mysql/conf.d/

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• SSH & SFTP: Should I assign one port to each user to facilitate bandwidth monitoring?

  - by BertS

  There is no easy way to track real-time per-user bandwidth usage for SSH and SFTP. I think assigning one port to each user may help. Idea of implementation Use case Bob, with UID 1001, shall connect on port 31001. Alice, with UID 1002, shall connect on port 31002. John, with UID 1003, shall connect on port 31003. (I do not want to lauch several sshd instances as proposed in question 247291.) 1. Setup for SFTP: In /etc/ssh/sshd_config: Port 31001 Port 31002 Port 31003 Subsystem sftp /usr/bin/sftp-wrapper.sh The file sftp-wrapper.sh starts the sftp server only if the port is the correct one: #!/bin/sh mandatory_port=3`id -u` current_port=`echo $SSH_CONNECTION | awk '{print $4}'` if [ $mandatory_port -eq $current_port ] then exec /usr/lib/openssh/sftp-server fi 2. Additional setup for SSH: A few lines in /etc/profile prevents the user from connecting on the wrong port: if [ -n "$SSH_CONNECTION" ] then mandatory_port=3`id -u` current_port=`echo $SSH_CONNECTION | awk '{print $4}'` if [ $mandatory_port -ne $current_port ] then echo "Please connect on port $mandatory_port." exit 1 fi fi Benefits Now it should be easy to monitor per-user bandwidth usage. A Rrdtool-based application could produce charts like this: I know this won't be a perfect calculation of the bandwidth usage: for example, if somebody launches a bruteforce attack on port 31001, there will be a lot of traffic on this port although not from Bob. But this is not a problem to me: I do not need an exact computation of per-user bandwidth usage, but an indicator that is approximately correct in standard situations. Questions Is the idea of assigning one port for each user is a good one? Is the proposed setup an reliable one? If I have to open dozens of ports for many users, should I expect a performance drawback? Do you know a rrdtool-based application which could make the chart above?

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• Many clients on a wireless AP for UDP broadcast packets

  - by distorteddisco

  I asked this question on StackOverflow and was directed over here, so I'd appreciate any advice. I'm deploying a smartphone application as part of a live music performance that depends on receiving UDP broadcast packets from a wireless access point. I'm guessing that between 20 and 50 clients will be connected at any one time. I'm aware that a maximum of 20 clients per access point is advised, but as the UDP broadcast packets are ground through the LAN, how would I be able to link multiple APs together? I'm looking for recommendations on a suitable AP for this. The actual data transmission rates are very low - only a few kB/s - as I'm just sending small messages to the smartphone apps, and there will be no WAN internet connection. I tried it with a few connected peers on an adhoc wireless connection without any problems, but ran into dropped packet issues on an old WRT54G running ddwrt, though it's in pretty rough shape. What's the best way to do this? I suppose I could limit concurrent wireless connections to 20 clients... but more would be nice. EDIT: I should also say that it's purely one-way communication; the smartphone application is only receiving broadcast packets, not sending anything.

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