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• Do RAID controllers commonly have SATA drive brand compatibility issues?

  - by Jeff Atwood

  We've struggled with the RAID controller in our database server, a Lenovo ThinkServer RD120. It is a rebranded Adaptec that Lenovo / IBM dubs the ServeRAID 8k. We have patched this ServeRAID 8k up to the very latest and greatest: RAID bios version RAID backplane bios version Windows Server 2008 driver This RAID controller has had multiple critical BIOS updates even in the short 4 month time we've owned it, and the change history is just.. well, scary. We've tried both write-back and write-through strategies on the logical RAID drives. We still get intermittent I/O errors under heavy disk activity. They are not common, but serious when they happen, as they cause SQL Server 2008 I/O timeouts and sometimes failure of SQL connection pools. We were at the end of our rope troubleshooting this problem. Short of hardcore stuff like replacing the entire server, or replacing the RAID hardware, we were getting desperate. When I first got the server, I had a problem where drive bay #6 wasn't recognized. Switching out hard drives to a different brand, strangely, fixed this -- and updating the RAID BIOS (for the first of many times) fixed it permanently, so I was able to use the original "incompatible" drive in bay 6. On a hunch, I began to assume that the Western Digital SATA hard drives I chose were somehow incompatible with the ServeRAID 8k controller. Buying 6 new hard drives was one of the cheaper options on the table, so I went for 6 Hitachi (aka IBM, aka Lenovo) hard drives under the theory that an IBM/Lenovo RAID controller is more likely to work with the drives it's typically sold with. Looks like that hunch paid off -- we've been through three of our heaviest load days (mon,tue,wed) without a single I/O error of any kind. Prior to this we regularly had at least one I/O "event" in this time frame. It sure looks like switching brands of hard drive has fixed our intermittent RAID I/O problems! While I understand that IBM/Lenovo probably tests their RAID controller exclusively with their own brand of hard drives, I'm disturbed that a RAID controller would have such subtle I/O problems with particular brands of hard drives. So my question is, is this sort of SATA drive incompatibility common with RAID controllers? Are there some brands of drives that work better than others, or are "validated" against particular RAID controller? I had sort of assumed that all commodity SATA hard drives were alike and would work reasonably well in any given RAID controller (of sufficient quality).

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• kvm and qemu host: Is there a limit for max CPUs (Ubuntu 10.04)?

  - by Valentin

  Today we encountered a really strange behaviour on two identical kvm and qemu hosts. The host systems each have 4 x 10 Cores, which means that 40 physical cores are displayed as 80 within the operating system (Ubuntu Linux 10.04 64 Bit). We started a Windows 2003 32 Bit VM (1 CPU, 1 GB RAM, we changed those values multiple times) on one of the nodes and noticed that it took 15 minutes until the boot process began. During those 15 minutes, a black screen is shown and nothing happens. libvirt and the host system show that the qemu-kvm process for the guest is almost idling. stracing this process only shows some FUTEX entries, but nothing special. After those 15 minutes, the Windows VM suddenly starts booting and the Windows logo occurs. After a few seconds, the VM is ready to be used. The VM itself is very performant, so this is no performance issue. We tried to pin the CPUs with the virsh and taskset tools, but this only made things worse. When we boot the Windows VM with a Linux Live CD there is also a black screen for several minutes, but not as long as 15. When booting another VM on this host (Ubuntu 10.04) it also has the black screen problem, and also here the black screen is only shown for 2-3 minutes (instead of 15). So, summerinzing this: Each guest on each of those identical nodes suffers from idling a few minutes after being started. After a few minutes, the boot process suddenly starts. We have observed that the idling time happens right after the bios of the guest was initialized. One of our employees had the idea to limit the amount of CPUs with maxcpus=40 (because of 40 physical cores existing) within Grub (kernel parameter) and suddenly the "black-screen-idling"-behaviour disappeared. Searching the KVM and Qemu mailing lists, the internet, forums, serverfault and other various sites for known bugs etc. showed no useful results. Even asking in the dev IRC channels brought no new ideas. The people there recommend us to use CPU pinning, but as stated before it didn't help. My question is now: Is there a sort of limit of CPUs for a qemu or kvm host system? Browsing the source code of those two tools showed that KVM would send a warning if your host has more than 255 CPUs. But we are not even scratching on that limit. Some stuff about the host system: 3.0.0-20-server kvm 1:84+dfsg-0ubuntu16+0.14.0+noroms+0ubuntu4 kvm-pxe 5.4.4-7ubuntu2 qemu-kvm 0.14.0+noroms-0ubuntu4 qemu-common 0.14.0+noroms-0ubuntu4 libvirt 0.8.8-1ubuntu6 4 x Intel(R) Xeon(R) CPU E7-4870 @ 2.40GHz, 10 Cores

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• what can cause a folder to become indestructible?

  - by JustJeff

  I have a directory that I want to delete, but windows (xp sp3) is giving me the run-around and the folder is now effectively indestructible. Attempts to open the folder, either via explorer or cmd.exe are met with 'd:/temp/foo Is Not Accessible. Access is denied'. Attempts to delete the folder result in 'Cannot delete foo: The directory is not empty' So I can't delete it because supposedly it's not empty, but windows won't let me in it for some reason, so I can't clean it out first. There's nothing in it of consequence, and basically I just want to delete it at this point. Thinking that some other process must have a lock on it, I used the SysInternals 'handles' and Process Explorer to look for open handles with the directory name. These turned up no matches. (The directory name is not actually 'foo', it is something more unique but 'foo' is easier to type here). I put the machine through a restart, and the problem persists. I did a search for the folder name with regedit, to see what other apps might be aware of it. No match. The properties dialog was mildly interesting. The Read-Only attribute is 'semi-checked', i.e., the grayish check mark you get when some parts are and some parts aren't. Naturally I immediately unchecked this, and tried to delete the folder. No go. Opening properties again reveals the gray check mark next to Read-Only has returned. All the stats, size, size on disk, files, folders, all these are zero. There do not appear to be any shares on the folder, so that's not it either. Finally, I tried opening the partition's properties, and running the Tools/Error Checking utility. This didn't turn up any problems either. Fwiw, this directory was created by [a popular gui zip tool] when I tried to unpack a tar-and-zipped archive created on another system with command line utils. The archive was definitely corrupt, but I've never seen such a file do anything worse than crash the zip app, and certainly never leave permanent glitches in the file system. So what else can possibly be going on to make this folder behave this way?

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• How to get more information from the system crash

  - by viraptor

  I'd like to debug an issue I'm having with a linux (debian stable) server, but I'm running out of ideas of how to confirm any diagnosis. Some background: The servers are running DL160 class with hardware raid between two disks. They're running a lot of services, mostly utilising network interface and CPU. There are 8 cpus and 7 "main" most cpu-hungry processes are bound to one core each via cpu affinity. Other random background scripts are not forced anywhere. The filesystem is writing ~1.5k blocks/s the whole time (goes up above 2k/s in peak times). Normal CPU usage for those servers is ~60% on 7 cores and some minimal usage on the last (whatever's running on shells usually). What actually happens is that the "main" services start using 100% CPU at some point, mainly stuck in kernel time. After a couple of seconds, LA goes over 400 and we lose any way to connect to the box (KVM is on it's way, but not there yet). Sometimes we see a kernel reporting hung task (but not always): [118951.272884] INFO: task zsh:15911 blocked for more than 120 seconds. [118951.272955] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [118951.273037] zsh D 0000000000000000 0 15911 1 [118951.273093] ffff8101898c3c48 0000000000000046 0000000000000000 ffffffffa0155e0a [118951.273183] ffff8101a753a080 ffff81021f1c5570 ffff8101a753a308 000000051f0fd740 [118951.273274] 0000000000000246 0000000000000000 00000000ffffffbd 0000000000000001 [118951.273335] Call Trace: [118951.273424] [<ffffffffa0155e0a>] :ext3:__ext3_journal_dirty_metadata+0x1e/0x46 [118951.273510] [<ffffffff804294f6>] schedule_timeout+0x1e/0xad [118951.273563] [<ffffffff8027577c>] __pagevec_free+0x21/0x2e [118951.273613] [<ffffffff80428b0b>] wait_for_common+0xcf/0x13a [118951.273692] [<ffffffff8022c168>] default_wake_function+0x0/0xe .... This would point at raid / disk failure, however sometimes the tasks are hung on kernel's gettsc which would indicate some general weird hardware behaviour. It's also running mysql (almost read-only, 99% cache hit), which seems to spawn a lot more threads during the system problems. During the day it does ~200kq/s (selects) and ~10q/s (writes). The host is never running out of memory or swapping, no oom reports are spotted. We've got many boxes with similar/same hardware and they all seem to behave that way, but I'm not sure which part fails, so it's probably not a good idea to just grab something more powerful and hope the problem goes away. Applications themselves don't really report anything wrong when they're running. I can run anything safely on the same hardware in an isolated environment. What can I do to narrow down the problem? Where else should I look for explanation?

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• Rsync: windows 7, synology: login error and permission denied error

  - by loonboon

  Good day to all of you all, I'm running into strange/stupid errors, and I hope anybody would be so kind to help me out. I have to admit, I am by no means a guru, so please bear with me :-) Situation: -Synology NAS (runs Linux), and Windows 7 desktop (1 normal/restricted user Lisa and 1 admin user). - Data from W7 desktop to be rsynced to synology: /volume1/home/Lisa/Backup - Rsync command: c:\cygwin\bin\rsync -avz /cygdrive/e/Lisa/ [email protected]:/volume1/homes/Lisa/Backup - I've set up ssh per these two threads: a. http://www.cesareriva.com/archives/102 b. http://www.cesareriva.com/archives/112 Now the horrors begin: - root is allowed to run the rsync succesfully, however, he doesn't login automatically (so I can not use rsync in W7 batchscripts, which is of course required). - Lisa is allowed to login automatically but he can not succesfully finish the rsync command because of permission errors: rsync change dir /volume1/homes/Lisa/Backup failed: permissions denied. This happens for each and every file and subdir rsync tries to create. However, the main directory (Backup) is created. When I try to copy files from windows explorer to the directory 'Backup' using the very same user Lisa everything goes smoothly. So, obviously, there is a permission problem somewhere; either my rsync-command isn't correct, or the folder permissions for homes/Lisa aren't correct (but, then again, Windows 7 copies files to that folder without any problems, so that does make me believe the homes/Lisa-permissions don't appear to be the problem). I also tried adding: --chmod=Dugo+x --chmod=ugo+r which I found somewhere on the web, to the rsync-command, but this didn't solve any problem and gave the exact errors. Would anybody please please help me on how to fix this? I am utterly frustrated about this, because I have been trying for 1 month to get everything to work and it simply doesn't work. I bought the big Synology to end the horrors of 20 external USB-disks for once and for all (we have many pictures and home vids of our deceased dogs and want to watch these, the horrors being 'what material is on what disk'). I'll gladly return the favour of somebody helping me out by buying you a nice beer (paypal), if you could end my misery. I am not extremely skilled on Linux (not at all :-( ) so if you could give an extra word when possible so I understand what to do, I'd be very grateful. I really hope somebody can help me out, Thank you in advance, Lisa

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• Best RAID setup for multimedia fileserver?

  - by Mr. Schwabe

  I'm building a fileserver for my small office. We do film and multimedia design. Only 3 clients connected. The server is primarily for local access to graphic assets and video files. I'm looking for advice on hardware and software required. Particularly for the RAID. I have the following objectives: A) merged capacity I'd like all other systems to access the data as a single mapped network drive that has an initial capacity of 10 TB. So perhaps 5x 2TB drives (plus mirror drives for redundancy). B) easy way to increase capacity Thinking long term, I'd like to 'easily' add more drives to the array for a potential two or three fold increase in capacity. So theoretically it could get upto a 30 TB raid array consisting of maybe 15x 2 TB drives of capacity (plus mirror drives for redundancy). C) maximum fault tolerance I want at least 1 mirror drive per capacity drive (in laymen's terms). So if I start with 10 TB / 5x 2TB of capacity, I suppose I would need another another 5x 2TB drives to be mirrors. So 10 drives total. But I'd also like potential for even more redundancy; with upto 2 additional mirrors per 'capacity drive' (and to be able to add them to the array anytime with ease). D) easy way to monitor drive health I'd like an intuitive interface for managing the raid and monitoring drive health The other systems accessing this network drive will be running Windows, but also the odd Ubuntu and MacOS system as well. Are these objectives attainable? What type of RAID setup do you recommend? What hardware will be required? Also what OS do you think this system should be running? Does it really matter? I'm no network admin - just a long time Windoze user, without much Linux experience. That said, I'm not opposed to a Linux solution if it's easy enough and more practical than a Windows OS for this server. Or maybe something such as Openfiler. Budget should hit the sweet spot for value and performance (hence my preference to use 2TB drives). The biggest focus is storage; aside from that the system just needs to keep the drives running optimally with perhaps 2 or 3 clients accessing / writing files at any given time. The hardware quote would start with something like 10x 2TB WD Caviar Blacks; about $1900 for the storage + $x for remaining parts. http://ncix.com/products/index.php?sku=42775&vpn=WD2001FASS&manufacture=Western%20Digital%20WD Your advice is appreciated, thanks!

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• Lag spikes at full CPU usage, maybe video card

  - by Roberts

  I am posting this thread in hurry so few things may be missed (I will update tomorrow). My PC specs: Motherboard Name - Gigabyte GA-945PL-S3 CPU Type - DualCore Intel Core 2 Duo E4300, 1800 MHz (9 x 200) OS - Microsoft Windows 7 Ultimate OS Kernel Type - 32-bit OS Version - 6.1.7601 I bougth a new video card one month ago. GeForce 210. I didn't have any problems. I wanted to overclock it, in other words: "Play with it". So I installed Gigabyte EasyBoost from CD and overclocked the GPU 590 + 110 mhz, memory to max to 960mhz from 800mhz. Benchmarks showed a little bit bigger score. Then I overclocked shader clock from 1405 to [..] (don't remeber really). So I was playing Modern Warfare 2 when off sudden computer froze when I wanted to select team, I was afk before that. I had to reset CMOS. After that I had problems with Skype: unread messages and no sound. Then I figured it out that when ever I open EasyBoost - Skype starts to glitch again. Now I use EVGA Precission X. Now after a month, I cleaned computer and closed the case, it was open all the time. I started to overclock GPU clock only (just a bit) because there was no problems that would stop me. So sometimes on heavy CPU load graphics starts to lag. Dragging a window is painful to watch too. Sometimes the screen freezes for 5 to 10 seconds (I can see that hard disk activity is maximal). You may say that CPU fault it is, isn't it? But sometimes lag spikes starts randomly when CPU load is at maximum. All 3 benchmark softwares (PerformanceTest, NovaBench and MSI Kombustor) shows that performance of my video card has dropped about 25%. BUT! CPU score is lower too. I ignored these problems but when I refreshed Windows Experience Index I was shocked. Month before (in latvian language but not so hard to understand): Now (upgraded RAM): This happened when I tried to capture Minecraft with Fraps on underclocked GPU to 580mhz (def: 590mhz): All drivers are up to date. Average CPU temperature from 55°C to 75°C (at 70°C sometimes starts these lag spikes). Video card's tempratures are from 45°C to 60°C (very hard to reach 60°C). So my hope is that the video card is fine, cause this card is very new and I want to upgrade CPU anyways. Aplogies for my mistakes in vocabulary (I am trying to type this as fast I can).

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• XP shared folders not accessible after BIOS changed

  - by stijn

  Here's what worked for over a year: PC A runs Windows 7, PC B runs Windows XP. Both are on the same subnet behind a router. A uses user account X, but logs in to PC B using the Administrator account. PC B is a Dell Precision 470. A known problem with these is that sometimes when plugging in their power cable they somehow loses all BIOS settings. This happened yesterday. After this happens Windows won't boot, because the default BIOS setting is 'RAID ON' while there is no RAID configured. No problem though, changing the BIOS settings to 'RAID OFF' makes it boot without problems. Note that in the meantime, nothing config-related was changed on machine A. It wasn't even on. Indeed after doing this, everything is fine. Everything includes all normal operations, remote desktop from PC A to PC B, running Synergy between A and B, accessing shared folders from B to A. But accessing the shared folders on B from A does not work any more. I tried pretty much everything I found via Google (fiddling with policies/registry kes/...) but no avail. > ping -a 192.168.2.2 Pinging A [192.168.2.2] with 32 bytes of data: Reply from 192.168.2.2: bytes=32 time<1ms TTL=128 > net view \\192.168.2.2 System error 5 has occurred. Access is denied. > net use /persistent:no K: \\A\myshare /user:A\USERNAME PASSWORD > net use /persistent:no K: \\192.168.2.2\myshare /user:192.168.2.2\USERNAME PASSWORD > net use /persistent:no K: \\192.168.2.2\myshare /user:USERNAME PASSWORD System error 86 has occurred. The specified network password is not correct. A solution to this would be great: I haven't been able to do any work since yesterday ;] update after taking the hard drive out of B and putting it in another Precision 470 with almost exactly the same hardware (at first sight, only the video card differs) the shared folders work.. Putting the disk back into A, same problem remains. Why does this depend on hardware, and more important, on which hardware?

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• Unecrypted Image of Truecrypt-Encrypted System Partition

  - by Dexter

  The general tenor around the internet seems to be that you can't create images of system partitions that have been encrypted (with truecrypt) other than with dd or similar sector-by-sector copy tools. These files however are very impractical given their size (and are obviously incompressible) which makes keeping multiple states/backups of your system partition rather expensive (..especially considering current hdd prices). The problem is that backup tools (like Acronis True Image, Clonezilla, etc.) won't give you the option to create an image of (mounted/opened) Truecrypt partitions, or that there is no recovery environment for restoring the backup, that would allow to run truecrypt before doing any actual restoring. After some trial and error however, I believe I have found a very simple way. Since Truecrypt (running in Linux) creates a virtual block device, that it uses for mounting the unencrypted partitions into the file system, partclone can be used for creating/restoring images. What I did: boot up a linux live disk mount/open the drive/device/partition in truecrypt unmount the filesystem mount point again, like so: umount /media/truecryptX ("X" being the partition number assigend by truecrypt) use partclone (this is what clonezilla would do too, except that clonezilla only offers you to back up real drive partitions, not virtual block devices): partclone.ntfs -c -s /dev/mapper/truecryptX -o nameOfBackupFile for restoring steps 1-3 remain the same, and step 4 is partclone.ntfs -r -s nameOfBackupFile -o /dev/mapper/truecryptX A backup and test-restore of the system (with this method) seems to have worked fine (and the changed settings were reverted to the backup-state). The backup file is ~40 GB (and compressible down to <8GB with 7zip/LZMA2 on the "fast" setting). I can't quite believe that I'm the only one that wants to create images of encrypted drives, but doesn't want to waste 100GB on the backup of one single system state. So my question now is, given how simple this was, and that no one seems to mention anywhere that this is possible - did I miss something? or did I do something wrong? Is there any situation that I didn't think of where this method will fail? Obviously, the backup file needs to be stored in some other encrypted place in order to still remain confidential, since it is unencrypted. Also, in order to do a full "bare metal" restore, one would have to actually first (re-)install Windows, encrypt it, and only then restore the backup file. The funny thing however is that you won't need to backup any partition tables, etc. since the reinstall will effectively take care of that. Is there anything else? This is imho still a lot better than having sector-by-sector images..

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• Can't connect to svnserve on localhost - connection actively refused

  - by RMorrisey

  When I try to connect using Tortoise to my SVN server using: svn://localhost/ Tortoise tells me: "Can't connect to host 'localhost'. No connection could be made because the target machine actively refused it." How can I fix this? I am trying to set up a subversion server on my local PC for personal use. I am running Windows Vista, with SlikSVN and TortoiseSVN installed. I previously had everything working correctly, but I found that I couldn't merge(!), apparently due to a version mismatch between the SVN client and server. Anyway... I now have the following setup: I created a repository using svnadmin create; it resides at C:\svnGrove C:\svnGrove\conf\svnserve.conf (# comments omitted): [general] anon-access=read auth-access=write password-db=passwd #authz-db=authz realm=svnGrove C:\svnGrove\conf\passwd: [users] myname=mypass My Subversion Server service is pointed to: C:\Program Files\SlikSvn\bin\svnserve.exe --service -r C:\svnGrove It shows the TCP/IP service as a dependency. I have also tried running svnserve from the command line, with similar results. The below is provided by the 'about' option in TortoiseSVN: TortoiseSVN 1.6.10, Build 19898 - 32 Bit , 2010/07/16 15:46:08 Subversion 1.6.12, apr 1.3.8 apr-utils 1.3.9 neon 0.29.3 OpenSSL 0.9.8o 01 Jun 2010 zlib 1.2.3 The following is from svn --version on the command line (not sure why it says CollabNet, CollabNet was the previous SVN binary that I had set up. The uninstaller failed to remove everything gracefully): svn, version 1.6.12 (SlikSvn/1.6.12) WIN32 compiled Jun 22 2010, 20:45:29 Copyright (C) 2000-2009 CollabNet. Subversion is open source software, see http://subversion.tigris.org/ This product includes software developed by CollabNet (http://www.Collab.Net/). The following repository access (RA) modules are available: * ra_neon : Module for accessing a repository via WebDAV protocol using Neon. - handles 'http' scheme - handles 'https' scheme * ra_svn : Module for accessing a repository using the svn network protocol. - with Cyrus SASL authentication - handles 'svn' scheme * ra_local : Module for accessing a repository on local disk. - handles 'file' scheme * ra_serf : Module for accessing a repository via WebDAV protocol using serf. - handles 'http' scheme - handles 'https' scheme I disabled my Windows Firewall and CA Internet Security, without success in resolving the issue. Edit The old version of svnserve was still set up as a service after the uninstall, pointed to this path: C:\Program Files\Subversion\svn-win32-1.4.6\bin I edited the registry key for the service to point to the new path (shown above). Whether I run svnserve as a service, or using -d, I do not see an entry for that port number in the listing generated by netstat -anp tcp.

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• Linux per-process resource limits - a deep Red Hat Mystery

  - by BobBanana

  I have my own multithreaded C program which scales in speed smoothly with the number of CPU cores.. I can run it with 1, 2, 3, etc threads and get linear speedup.. up to about 5.5x speed on a 6-core CPU on a Ubuntu Linux box. I had an opportunity to run the program on a very high end Sunfire x4450 with 4 quad-core Xeon processors, running Red Hat Enterprise Linux. I was eagerly anticipating seeing how fast the 16 cores could run my program with 16 threads.. But it runs at the same speed as just TWO threads! Much hair-pulling and debugging later, I see that my program really is creating all the threads, they really are running simultaneously, but the threads themselves are slower than they should be. 2 threads runs about 1.7x faster than 1, but 3, 4, 8, 10, 16 threads all run at just net 1.9x! I can see all the threads are running (not stalled or sleeping), they're just slow. To check that the HARDWARE wasn't at fault, I ran SIXTEEN copies of my program independently, simultaneously. They all ran at full speed. There really are 16 cores and they really do run at full speed and there really is enough RAM (in fact this machine has 64GB, and I only use 1GB per process). So, my question is if there's some OPERATING SYSTEM explanation, perhaps some per-process resource limit which automatically scales back thread scheduling to keep one process from hogging the machine. Clues are: My program does not access the disk or network. It's CPU limited. Its speed scales linearly on a single CPU box in Ubuntu Linux with a hexacore i7 for 1-6 threads. 6 threads is effectively 6x speedup. My program never runs faster than 2x speedup on this 16 core Sunfire Xeon box, for any number of threads from 2-16. Running 16 copies of my program single threaded runs perfectly, all 16 running at once at full speed. top shows 1600% of CPUs allocated. /proc/cpuinfo shows all 16 cores running at full 2.9GHz speed (not low frequency idle speed of 1.6GHz) There's 48GB of RAM free, it is not swapping. What's happening? Is there some process CPU limit policy? How could I measure it if so? What else could explain this behavior? Thanks for your ideas to solve this, the Great Xeon Slowdown Mystery of 2010!

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• Different files on shared partition?

  - by Matt Robertson

  I am dual-booting Windows 8 and Ubuntu 12.04. My partition scheme looks like this: /dev/sda1 - Windows 8 (nfts) /dev/sda2 - Ubuntu / (ext4) /dev/sda3 - Ubuntu home (ext4) /dev/sda5 - swap /dev/sda6 - Shared data partition (exfat) (First off, yes I do have exfat libraries installed on Ubuntu) I created some PNG images in Windows and saved them on my shared partition. From Ubuntu, I edited the images in GIMP and saved them (replacing the ones on the shared partition). When I boot into Windows, the files appear unchanged - exactly like they did before I edited them from Ubuntu. I even added a folder and deleted some other files, but none of these changes exist in Windows. When I boot into Ubuntu, all of the changes are still there. It is as if Windows is caching the old file structure... How is this possible? Thanks in advance. Edit -- commands output ~~ lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 465.8G 0 disk +-sda1 8:1 0 165.1G 0 part +-sda2 8:2 0 21.3G 0 part / +-sda3 8:3 0 98.9G 0 part /home +-sda4 8:4 0 1K 0 part +-sda5 8:5 0 7.8G 0 part [SWAP] +-sda6 8:6 0 172.7G 0 part /mnt/shared_data ~~ /etc/fstab # <file system> <mount point> <type> <options> <dump> <pass> proc /proc proc nodev,noexec,nosuid 0 0 # /dev/sda2 UUID=8f700f65-b5c7-4afc-a6fb-8f9271e0fb5e / ext4 errors=remount-ro 0 1 # /dev/sda3 UUID=f0d688b7-22bd-4fa7-bc1b-a594af2933fa /home ext4 defaults 0 2 # /dev/sda5 UUID=3bc2399b-5deb-4f04-924b-d4fc77491997 none swap sw 0 0 # /dev/sda6 UUID=F2DE-BC47 /mnt/shared_data exfat defaults 0 3 ~~ /etc/mtab /dev/sda2 / ext4 rw,errors=remount-ro 0 0 proc /proc proc rw,noexec,nosuid,nodev 0 0 sysfs /sys sysfs rw,noexec,nosuid,nodev 0 0 none /sys/fs/fuse/connections fusectl rw 0 0 none /sys/kernel/debug debugfs rw 0 0 none /sys/kernel/security securityfs rw 0 0 udev /dev devtmpfs rw,mode=0755 0 0 devpts /dev/pts devpts rw,noexec,nosuid,gid=5,mode=0620 0 0 tmpfs /run tmpfs rw,noexec,nosuid,size=10%,mode=0755 0 0 none /run/lock tmpfs rw,noexec,nosuid,nodev,size=5242880 0 0 none /run/shm tmpfs rw,nosuid,nodev 0 0 /dev/sda3 /home ext4 rw 0 0 /dev/sda6 /mnt/shared_data fuseblk rw,nosuid,nodev,allow_other,blksize=4096 0 0 binfmt_misc /proc/sys/fs/binfmt_misc binfmt_misc rw,noexec,nosuid,nodev 0 0 gvfs-fuse-daemon /home/matt/.gvfs fuse.gvfs-fuse-daemon rw,nosuid,nodev,user=matt 0 0

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• Kernel-mode Authentication: 401 errors when accessing site from remote machines

  - by CJM

  I have several Classic ASP sites that use Integrated Windows Authentication and Kerberos delegation. They work OK on the live servers (recently moved to a Server 2008/IIS7 servers), but do not work fully on my development PC or my development server. The IIS on both machines were configured through an IIS web deployment tool package which was exported from an old machine; the deployment didn't work perfectly, and I had to tinker a bit to get the sites working. When accessing the apps locally on either machine, they work fine; when accessing from another machine, the user is prompted by a username/password dialog, and regardless of what you enter, ultimately it results in a 401 (Unauthorised) error. I've tried comparing the configuration of these machines against similar live servers (that all work fine), and they seem generally comparable (given that none of the live servers are yet on IIS7.5 (Windows 7/Server 2008 R2). These applications run in a common application pool which uses a special domain user as it's identity - this user has similar permissions on the live and development machines. On IIS6 platforms, to enable kerberos delegation, I needed to set up some SPNs for this user, and they are still in place (even though I don't believe they are needed any longer for IIS7+ due to kernel-mode authentication), Furthermore, this account is enabled for Kerberos delegation in Active Directory, as is each machine I am dealing with. I'm considering the possibility that the deployment might have made changes/failed to make changes to the IIS configuration thus causing this problem. Perhaps a complete rebuild (minus another web deployment attempt) would solve the problem, but I'd rather fix (thus understand) the current problem. Any ideas so far? I've just had another attempt at fixing this issue, and I've made some progress, but I don't have a complete fix...yet. I've discovered that if I access the sites via IP address (than via NetBIOS name), I get the same dialog, except that it accepts my credentials and thus the application works - not quite a fix, but a useful step. More interestingly, I discovered that if I disable Kernel-mode authentication (in IIS Manager Website Authentication Advanced Settings), the applications work perfectly. My foggy understanding is that this is effectively working in the pre-IIS7 way. A reasonable short-term solution, but consider the following explicit advice from IIS on this issue: By default, IIS enables kernel-mode authentication, which may improve authentication performance and prevent authentication problems with application pools configured to use a custom identity. As a best practice, do not disable this setting if Kerberos authentication is used in your environment and the application pool is configured to use a custom identity. Clearly, this is not the way my applications should be working. So what is the issue?

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• load-causing processes disappearing from "top" ps -o pcpu shows bogus numbers

  - by Alec Matusis

  I administer a large number of servers, and I have this problem only with Ubuntu 10.04 LTS: I run a server under normal load (say load average 3.0 on an 8-core server). The "top" command shows processes taking certain % of CPU that cause this load average: say PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 11008 mysql 20 0 25.9g 22g 5496 S 67 76.0 643539:38 mysqld ps -o pcpu,pid -p11008 %CPU PID 53.1 11008 , everything is consistent. The all of the sudden, the process causing the load average disappears from "top", but the process continues to run normally (albeit with a slight performance decrease), and the system load average becomes somewhat higher. The output of ps -o pcpu becomes bogus: # ps -o pcpu,pid -p11008 %CPU PID 317910278 1587 This happened to at least 5 different severs (different brand new IBM System X hardware), each running different software: one httpd 2.2, one mysqld 5.1, and one Twisted Python TCP servers. Each time the kernel was between 2.6.32-32-server and 2.6.32-40-server. I updated some machines to 2.6.32-41-server, and it has not happened on those yet, but the bug is rare (once every 60 days or so). This is from an affected machine: top - 10:39:06 up 73 days, 17:57, 3 users, load average: 6.62, 5.60, 5.34 Tasks: 207 total, 2 running, 205 sleeping, 0 stopped, 0 zombie Cpu(s): 11.4%us, 18.0%sy, 0.0%ni, 66.3%id, 4.3%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 74341464k total, 71985004k used, 2356460k free, 236456k buffers Swap: 3906552k total, 328k used, 3906224k free, 24838212k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 805 root 20 0 0 0 0 S 3 0.0 1493:09 fct0-worker 982 root 20 0 0 0 0 S 1 0.0 111:35.05 fioa-data-groom 914 root 20 0 0 0 0 S 0 0.0 884:42.71 fct1-worker 1068 root 20 0 19364 1496 1060 R 0 0.0 0:00.02 top Nothing causing high load is showing on top, but I have two highly loaded mysqld instances on it, that suddenly show crazy %CPU: #ps -o pcpu,pid,cmd -p1587 %CPU PID CMD 317713124 1587 /nail/encap/mysql-5.1.60/libexec/mysqld and #ps -o pcpu,pid,cmd -p1624 %CPU PID CMD 2802 1624 /nail/encap/mysql-5.1.60/libexec/mysqld Here are the numbers from # cat /proc/1587/stat 1587 (mysqld) S 1212 1088 1088 0 -1 4202752 14307313 0 162 0 85773299069 4611685932654088833 0 0 20 0 52 0 3549 27255418880 5483524 18446744073709551615 4194304 11111617 140733749236976 140733749235984 8858659 0 552967 4102 26345 18446744073709551615 0 0 17 5 0 0 0 0 0 the 14th and 15th numbers according to man proc are supposed to be utime %lu Amount of time that this process has been scheduled in user mode, measured in clock ticks (divide by sysconf(_SC_CLK_TCK). This includes guest time, guest_time (time spent running a virtual CPU, see below), so that applications that are not aware of the guest time field do not lose that time from their calculations. stime %lu Amount of time that this process has been scheduled in kernel mode, measured in clock ticks (divide by sysconf(_SC_CLK_TCK). On a normal server, these numbers are advancing, every time I check the /proc/PID/stat. On a buggy server, these numbers are stuck at a ridiculously high value like 4611685932654088833, and it's not changing. Has anyone encountered this bug?

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• long access times and errors in iis application

  - by Jens Olsson

  Hi, I am having an issue with an IIS application (details of environment at the end of the message). The web site works great most of the time and I cannot reproduce any error in our test system. On the live system however with on averare of 5-15 requests per second I have a problem with that some requests (about 0.05%) will take over 300 seconds to complete. The other requests complete withing 5-10 seconds. It seem like if all the errornous requests end up with a Timer_EntityBody error in the error log. I have never seen this as an end user but I guess that they will receive some kind of error message. I am trying to find out what can be causing this errornous behaviour. Any ideas are welcome. I have read something about that there can be an MTU issue if ICMP and MTU protocols are blocked in the firewall. Does that sound reasonable? I have also read about updating to IIS 7 should do the trick. Does it sound reasonable? I think that the problem has another cause but I have no idea of what. I have tried running hte perormance monitor, monitoring for database locks and active transaction counts. I can see some of these in the perfmon log for the MSSQL server (another machine) for example: Active transactions is sometimes peaking and sometimes for long periods Lock waits per seconds is sometimes peaking Transactions per second is sometimes peaking Page IO Latch wait is sometimes peaking Lock wait time (ms) is sometimes peaking But I cannot see that any of these correlate to the errors in the IIS error log. On the IIS server machine I can also see with perfmon that some values peak a few times during a day: Request execution time Avg disk queue length I can neither see that any of these correlate to the errors in the IIS error log. In the below code I have anonymized by replacing some parts with HIDDEN The following can be seen in the access log 2010-10-01 08:35:05 W3SVC1301873091 **HIDDEN** POST /**HIDDEN**/Modules/BalanceModule.aspx - 80 - **HIDDEN** Mozilla/4.0+(compatible;+MSIE+7.0;+Windows+NT+5.1;+.NET+CLR+2.0.50727;+.NET+CLR+3.0.4506.2152;+.NET+CLR+3.5.30729;+.NET4.0C;+.NET4.0E) ASP.NET_SessionId=**HIDDEN** 400 0 64 0 2241 127799 At the same time the following can be seen in the error log: 2010-10-01 08:35:05 **HIDDEN** 1999 **HIDDEN** 80 HTTP/1.0 POST /**HIDDEN**/Modules/BalanceModule.aspx - 1301873091 Timer_EntityBody Test+Pool I can tell the following about the environment: Server: Windows Server 2003 x64 SP2 running on VMWare HTTP Server: IIS v6.0 with ASP.NET 2.0.50727 Antivirus: Trend Micro OfficeScan (Is it a good idea to have this on a server?)

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• Radeon HD4850 serious issues when using DirectX 10

  - by ricsmania

  Hello, I have a problem with my video card. Whenever I run a DirectX 10 game, it works for a few seconds (10 or so) and then starts displaying nothing but big polygons. I have tested this with Crysis and Resident Evil 5, both have the same problems. The same games running under DirectX 9 work fine, except for some small black squares once in a while. I have the following specs: Asus P7P55D LE Intel Core i5 750 Sapphire Radeon HD4850 1GB 2x2GB Patriot Viper II Sector 5, DDR3 1600 MHz OCZ Stealth X Stream 500SXS 500W At first I thought it could be the video card overheating (it has stock cooling), but the game crashes even when it's running at 50 degrees C, and it's never been higher than 70. I also thought it could be the PSU, but as far as I know 500W is enough for this computer, especially because I haven't overclocked anything. My OS is Windows 7 X64 and I am using Catalyst 10.10, but I have also tried many older versions with no success. I don't think there is a problem with the card itself, or else it wouldn't run DirectX 9 games I believe. I have spent many hours searching for a solution but I couldn't, so any help is appreciated. Thank you. EDIT: I did some further investigation about the problem, and it seems taspeotis was right, it might be related to memory. I slightly underclocked the memory from 993 to 965 MHz and the problem went away completely. Both the black squares using DirectX 9 and the weird polygons using DirectX 10. I was using RE DirectX 10 Benchmark, as it consistently crashed around the same point, and now I can play the full benchmark with no artifacts at all. Unfortunately, the underclock has an obvious hit in performance. Although it's not critical, it's definitely noticeable. So, if the video memory test software showed no erros, but the card needs an underclock to work, what might be the problem? Temperature? Voltage? By the way, I couldn't find what the default voltage for this card is. And what is a good software to try and increase it? I tried Ati Tray Tools but it has a bug that increases the clock speed dramatically whenever I change something in the Overclock tab, so I'm afraid it might fry my card. Worst case scenario, if I don't find I solution I will try to slightly increase the GPU clock to compensate for the memory clock. Thank you again.

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• Microsoft Office 2003 document (Excel and Word) intermitently, takes 30 seconds to load

  - by Julio Nobre

  I am trying to figure out why a simple .XLS EXCEL workbook is taking, randomly, 30 seconds to open. Before answering: Please, bear mind the following: Problem symptoms Hanging is intermitent and it takes exactly 30 seconds; During hanging there is no cpu or disk activity; It only happens during document load. Every runs smooth after that; Windows Explorer.exe hangs on folder, but all other folders, system and applications are still responsive; There are no consecutive hangings. I have to wait for while to reproduce this behaviour; All samples documents are located on a local drive (C:\BPI); The no document has has macros and have any addins usage; The problem does occurs on others files extensions like .PDF, for example; Office 2003 is being used for several years; The computer is running Windows XP; Computer has several network mapped drives, all addressed to main file server; Recently, main fileserver was replaced by Windows 2011 SBS Standard Edition What I have done so far I have traced machine Explorer.exe, using Process Monitor, added Duration column, and filtered by Duration 1. That's is how I found that hanging was taking exactly 30 seconds. For further information, please refer to Oliver Salzburg tutorial. Using Process Monitor, I have also figured out than five operations were taking most of sample collecting duration. Looking at sample image below, column Operation below you will notice that one single operation was taking 29 seconds; I have tried different documents (.xls and .doc), all of them smaller than 30 KB; I have, temporarily, removed all shortcuts on User Document's folder that were pointing to network drives or shares; I have runned CCleaner to fix registry issues; I made sure that there were no external links on tested workbook or word documents; I have reproduced this behaviour for hours; I have extensivelly researched for hours on the web; Process Monitor's collected and filtered data

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• How to get an inactive RAID device working again?

  - by Jonik

  After booting, my RAID1 device (/dev/md_d0 *) sometimes goes in some funny state and I cannot mount it. * Originally I created /dev/md0 but it has somehow changed itself into /dev/md_d0. # mount /opt mount: wrong fs type, bad option, bad superblock on /dev/md_d0, missing codepage or helper program, or other error (could this be the IDE device where you in fact use ide-scsi so that sr0 or sda or so is needed?) In some cases useful info is found in syslog - try dmesg | tail or so The RAID device appears to be inactive somehow: # cat /proc/mdstat Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] md_d0 : inactive sda4[0](S) 241095104 blocks # mdadm --detail /dev/md_d0 mdadm: md device /dev/md_d0 does not appear to be active. Question is, how to make the device active again (using mdmadm, I presume)? (Other times it's alright (active) after boot, and I can mount it manually without problems. But it still won't mount automatically even though I have it in /etc/fstab: /dev/md_d0 /opt ext4 defaults 0 0 So a bonus question: what should I do to make the RAID device automatically mount at /opt at boot time?) This is an Ubuntu 9.10 workstation. Background info about my RAID setup in this question. Edit: My /etc/mdadm/mdadm.conf looks like this. I've never touched this file, at least by hand. # by default, scan all partitions (/proc/partitions) for MD superblocks. # alternatively, specify devices to scan, using wildcards if desired. DEVICE partitions # auto-create devices with Debian standard permissions CREATE owner=root group=disk mode=0660 auto=yes # automatically tag new arrays as belonging to the local system HOMEHOST <system> # instruct the monitoring daemon where to send mail alerts MAILADDR <my mail address> # definitions of existing MD arrays # This file was auto-generated on Wed, 27 Jan 2010 17:14:36 +0200 In /proc/partitions the last entry is md_d0 at least now, after reboot, when the device happens to be active again. (I'm not sure if it would be the same when it's inactive.) Resolution: as Jimmy Hedman suggested, I took the output of mdadm --examine --scan: ARRAY /dev/md0 level=raid1 num-devices=2 UUID=de8fbd92[...] and added it in /etc/mdadm/mdadm.conf, which seems to have fixed the main problem. After changing /etc/fstab to use /dev/md0 again (instead of /dev/md_d0), the RAID device also gets automatically mounted!

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• Operative systems on SD cards

  - by HisDudeness

  I was getting some wild ideas the last days, like putting some operative systems into SD cards rather than on my hard drive. I'll go further into details now and explain what lead me to consider this probably abominable decision. I am on a laptop (that means I have a native SD-card reader) which is currently running a cross-distro setup, with a bunch of Linux systems (placed in dedicated ext4 logical partitions into a huge extended one) regulated by an unique GRUB. Since today, my laptop haven't even seen any Windows system with binoculars. I was thinking about placing all the os part of my setup into a Secure Digital to save all my 500 Gb Hard Drive for documents, music, videos and so on, and being able to just remove the SD and boot my system into another computer too, as well as having the possibility of booting other systems into mine by just plugging in another SD, without having to keep it constantly placed in my PC. Also, in the remote case in the near future I just wanted to boot Windows 8 in it, I read it causes major boot incompatibility issues with other systems by needing a digital signature in order for them to start. By having it in a removable drive, I could just get rid of it when I'm needing him and switch its card with Linux one, and so not having any obstacles to their boot. Now, my questions are: I know unlikely traditional rotating disk drives, integrated circuits ones have a limited lifespan in terms of cluster rewriting. Is it an obstacle to that kind of usage? I mean, some Ultrabooks are using SSD now, is it the same issue, or there are some differences between Solid State Drives and Secure Digitals in that sense? Maybe having them to store system files which are in fixed positions (making the even-usage of cluster technology useless) constantly being re-read and updated and similar things just gets them soon unserviceable, do it? Second question: are all motherboards and BIOSes able to boot from SDs just like they are from USB pen drives (I mean, provided card reader is USB-connected, isn't it)? Or can't bootloaders like GRUB be installed on SDs working? If they can't, is it a solution installing GRUB to MBR and making boot option pointing to SD? Will it work? Are there any other problems to installing OSs on a Secure Digital?

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• serving mp3s to mobile devices is flooding nginx with partial requests

  - by drumfire

  I am serving mp3s with a minimalistic nginx server. What I see in my log files is that there are a lot of requests, in particular from AppleCoreMedia and sometimes Android useragents, that flood the server with short requests. Sometimes they keep requesting to download the same partial content for a very long time; sometimes more than an hour. For example: "GET /somefile.mp3 HTTP/1.1" 206 33041 "AppleCoreMedia/1.0.0.9B206 (iPhone; U; CPU OS 5_1_1 like Mac OS X; en_us)" "GET /somefile.mp3 HTTP/1.1" 206 33041 "AppleCoreMedia/1.0.0.9B206 (iPhone; U; CPU OS 5_1_1 like Mac OS X; en_us)" "GET /somefile.mp3 HTTP/1.1" 206 33041 "AppleCoreMedia/1.0.0.9B206 (iPhone; U; CPU OS 5_1_1 like Mac OS X; en_us)" [...] I also get a lot, but not as much, of these: "-" 400 0 "-" "-" 400 0 "-" The IP addresses are always from clients that start downloading shortly after that request, usually they have roughly the same UserAgent as in the first example. emphasized text I have enabled server throttling and connection limits in nginx to limit the huge amount of log entries from equivalent IPs at least somewhat. There was a performance issue when I saw the same behaviour on the previous server that used Apache. I installed nginx on a better server then moved the site. When Apache could not handle more connections from the increasing number of clients effectively that server was ddossed. There was no bandwidth issue with already connected clients and I don't know if the already connected clients were using more than one connection at a time. Please tell me: Are clients that appear to get stuck on a download a Bad Thing™ I heard people say their mobile bandwidth use was much higher than they could account for. I'm thinking this type of client behaviour can account for that. And costs us more bandwidth too. Which up to date alternatives exist out there that can handle serving this type of data better than plain HTTP? Useful general insights for someone who just came into this field straight out of the late 90s. :-)

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• Is this distributed database server idea feasible?

  - by David

  I often use SQLite for creating simple programs in companies. The database is placed on a file server. This works fine as long as there are not more than about 50 users working towards the database concurrently (though depending on whether it is reads or writes). Once there are more than this, they will notice a slowdown if there are a lot of concurrent writing on the server as lots of time is spent on locks, and there is nothing like a cache as there is no database server. The advantage of not needing a database server is that the time to set up something like a company Wiki or similar can be reduced from several months to just days. It often takes several months because some IT-department needs to order the server and it needs to conform with the company policies and security rules and it needs to be placed on the outsourced server hosting facility, which screws up and places it in the wrong localtion etc. etc. Therefore, I thought of an idea to create a distributed database server. The process would be as follows: A user on a company computer edits something on a Wiki page (which uses this database as its backend), to do this he reads a file on the local harddisk stating the ip-address of the last desktop computer to be a database server. He then tries to contact this computer directly via TCP/IP. If it does not answer, then he will read a file on the file server stating the ip-address of the last desktop computer to be a database server. If this server does not answer either, his own desktop computer will become the database server and register its ip-address in the same file. The SQL update statement can then be executed, and other desktop computers can connect to his directly. The point with this architecture is that, the higher load, the better it will function, as each desktop computer will always know the ip-address of the database server. Also, using this setup, I believe that a database placed on a fileserver could serve hundreds of desktop computers instead of the current 50 or so. I also do not believe that the load on the single desktop computer, which has become database server will ever be noticable, as there will be no hard disk operations on this desktop, only on the file server. Is this idea feasible? Does it already exist? What kind of database could support such an architecture?

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• Force caching of handler output which actively resists caching

  - by deceze

  I'm trying to force caching of a very obnoxious piece of PHP script which actively tries to resist caching for no good reason by actively setting all the anti-cache headers: Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0 Content-Type: text/html; charset=UTF-8 Date: Thu, 22 May 2014 08:43:53 GMT Expires: Thu, 19 Nov 1981 08:52:00 GMT Last-Modified: Pragma: no-cache Set-Cookie: ECSESSID=...; path=/ Vary: User-Agent,Accept-Encoding Server: Apache/2.4.6 (Ubuntu) X-Powered-By: PHP/5.5.3-1ubuntu2.3 If at all avoidable I do not want to have to modify this 3rd party piece of code at all and instead just get Apache to cache the page for a while. I'm doing this very selectively to only very specific pages which have no real impact on session cookies or the like, i.e. which do not contain any personalised information. CacheDefaultExpire 600 CacheMinExpire 600 CacheMaxExpire 1800 CacheHeader On CacheDetailHeader On CacheIgnoreHeaders Set-Cookie CacheIgnoreCacheControl On CacheIgnoreNoLastMod On CacheStoreExpired On CacheStoreNoStore On CacheLock On CacheEnable disk /the/script.php Apache is caching the page alright: [cache:debug] AH00698: cache: Key for entity /the/script.php?(null) is http://example.com:80/the/script.php? [cache_disk:debug] AH00709: Recalled cached URL info header http://example.com:80/the/script.php? [cache_disk:debug] AH00720: Recalled headers for URL http://example.com:80/the/script.php? [cache:debug] AH00695: Cached response for /the/script.php isn't fresh. Adding conditional request headers. [cache:debug] AH00750: Adding CACHE_SAVE filter for /the/script.php [cache:debug] AH00751: Adding CACHE_REMOVE_URL filter for /the/script.php [cache:debug] AH00769: cache: Caching url: /the/script.php [cache:debug] AH00770: cache: Removing CACHE_REMOVE_URL filter. [cache_disk:debug] AH00737: commit_entity: Headers and body for URL http://example.com:80/the/script.php? cached. However, it is always insisting that the "cached response isn't fresh" and is never serving the cached version. I guess this has to do with the Expires header, which marks the document as expired (but I don't know whether that's the correct assumption). I've tried to overwrite and unset headers using mod_headers, but this doesn't help; whatever combination I try the cache is not impressed at all. I'm guessing that the order of operation is wrong, and headers are being rewritten after the cache sees them. early header processing doesn't help either. I've experimented with CacheQuickHandler Off and trying to set explicit filter chains, but nothing is helping. But I'm really mostly poking in the dark, as I do not have a lot of experience with configuring Apache filter chains. Is there a straight forward solution for how to cache this obnoxious piece of code?

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• Should use EXT4 or XFS to be able to 'sync'/backup to S3?

  - by Rafa

  It's my first message here, so bear with me... (I have already checked quite a few of the "Related Questions" suggested by the editor) Here's the setup, a brand new dedicated server (8GB RAM, some 140+ GB disk, Raid 1 via HW controller, 15000 RPM) it's a production web server (with MySQL in it, too, not just serving web requests); not a personal desktop computer or similar. Ubuntu Server 64bit 10.04 LTS We have an Amazon EC2+EBS setup with the EBS volume formatted as XFS for easily taking snapshots to S3, via AWS' console. We are now migrating to the dedicated server and I want to be able to backup our data to Amazon's S3. The main reason being the possibility of using the latest snapshot from an EC2 instance in case of hardware failure on the dedicated server. There are two approaches I am thinking of: do a "simple" file-based backup with rsync, dumping the database' and other files, and uploading to amazon via S3 API commands, or to an EC2 instance, or something. do a file-system "freeze" (using XFS) with the usual ebs/ec2 snapshot tool to take part of the file system, take a snapshot, and upload it to Amazon. Here's my question (or series of questions): Can I safely use XFS for the whole system as the main and only format on the dedicated server? If not, is it safe to use EXT4? Or should I use something else? would then be possible to make snapshots of the system to upload to Amazon? Is it possible/feasible/practical to do what I want to do, anyway? any recommendations? When searching around for S3/EBS/XFS, anything relevant to my problem is usually focused on taking snapshots of a XFS system that is already an EBS volume. My intention is to do it in a "real"/metal dedicated server. Update: I just saw this on Wikipedia: XFS does not provide direct support for snapshots, as it expects the snapshot process to be implemented by the volume manager. I had always assumed that I could choose 2 ways of doing snapshots: via LVM or via XFS (without LVM). After reading this, I realize these 2 options are more like it: With XFS: 1) do xfs_freeze; 2) copy the frozen files via, eg, rsync; 3) unfreeze xfs With LVM and XFS: 1) do xfs_freeze; 2) make a binary copy of the frozen fs via lvcreate and related commands; 3) unfreeze xfs; 4) somehow backup the LVM snapshot. Thanks a lot in advance, Let me know if I need to clarify something.

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• force unattended install php apt debian squeeze

  - by user1258619

  i am trying to do an unattended install via php for several packages but every time when the dependencies come up it aborts instead of forcing the answer to be yes. (i have broken apt a few times...) each time though i start off re-imaging my vps(testing server) so there isn't an issue of something still being hung or crashed.can someone tell me what i am doing wrong? keep in mind this is the 12th version of this script to get nowhere. fwrite(STDOUT, "Root Password:\n"); $root_pass = chop(fgets(STDIN)); $file_apt = '/etc/apt/apt.conf.d/70debconf'; // Open the file to get existing content $current_apt = file_get_contents($file_apt); // Append a new person to the file $current_apt .= "Dpkg::Options {\"--force-confold\";};\n"; // Write the contents back to the file file_put_contents($file_apt, $current_apt); $update = shell_exec('echo '.$root_pass.' | DEBIAN_FRONTEND=noninteractive sudo -S apt-get update'); echo $update; $update_upgrade = shell_exec('echo '.$root_pass.' | DEBIAN_FRONTEND=noninteractive sudo -s apt-get upgrade'); echo $update_upgrade; $install_unattended_mysql = shell_exec('echo '.$root_pass.' | DEBIAN_FRONTEND=noninteractive apt-get install --yes --force-yes mysql-server'); echo $install_unattended_mysql; $install_mysql_set_password = shell_exec('mysql -u root -e "UPDATE mysql.user SET password=PASSWORD("'.$root_pass.'") WHERE user="root"; FLUSH PRIVILEGES;'); echo $install_mysql_set_password; i have read a few places that i needed to edit the apt.conf file so i am doing so here and doing an update and an upgrade. also the upgrade does abort when it actually has to install something. The following packages will be upgraded: apache2 apache2-doc apache2-mpm-prefork apache2-utils apache2.2-bin apache2.2-common base-files bind9 bind9-host bind9utils debian-archive-keyring dpkg dselect libbind9-60 libc-bin libc6 libdns69 libisc62 libisccc60 libisccfg62 liblwres60 locales 22 upgraded, 0 newly installed, 0 to remove and 0 not upgraded. Need to get 18.4 MB of archives. After this operation, 8192 B of additional disk space will be used. Do you want to continue [Y/n]? Abort. I also should note that only a few pieces of software are going to be installed from the apt repo's as i will include some binaries to go along with it.

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• How to rate-limit concurrent sessions with nginx or haproxy?

  - by bantic

  I'm currently using nginx to reverse-proxy requests from web clients that are doing long-polling to an upstream. Since we're doing long polling (as opposed to websockets), when a client connects it will make multiple http connections to the server in serial, re-establishing a connection every time the server sends it some data (or timing out and re-establishing if the server has nothing to say for 10 seconds). What I'd like to do is limit the number of concurrent web clients. Since the clients are constantly making new HTTP requests instead of keeping a single request open, it's a little tricky to count the total number of web clients (because it's not the same as total number of concurrently connected http clients). The method I've come up with is to track http requests by the originating IP address, and store the IP address somewhere with a TTL of 20 seconds. If a request comes in whose IP isn't recognized, then we check the total number of unexpired stored IP addresses; if that's less than the maximum then we allow this request through. And if a request comes in with an IP address that we can find in the look-up table that hasn't yet expired, then it is allowed through as well. All requests that are allowed through have their IPs added to the table (if not there before) and the TTL refreshed to 20 seconds again. I had actually whipped something together that worked correctly this way using nginx along with the Redis 2.0 Nginx Module (and the nginx lua module to simplify the conditional branching), using redis to store my IP addresses with a TTL (the SETEX command), and checking the table size with the DBSIZE command. This worked but the performance was horrible. nginx and redis ended up using lots of cpu and the machine could only handle a very small number of concurrent requests. The new stick-table and tracking counters that were added to Haproxy in version 1.5 (via a commission from serverfault) seem like they might be ideal to implement exactly this sort of rate limiting, because the stick-table can track IP addresses and automatically expire entries. However, I don't see an easy way to get a total count of the unexpired entries in the stick table, which would be necessary to know the number of connected web clients. I'm curious if anyone has any suggestions, for nginx or haproxy or even for something else not mentioned here that I haven't thought of yet.

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