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• mounting ext4 fs with block size of 65536

  - by seaquest

  I am doing some benchmarking on EXT4 performance on Compact Flash media. I have created an ext4 fs with block size of 65536. however I can not mount it on ubuntu-10.10-netbook-i386. (it is already mounting ext4 fs with 4096 bytes of block sizes) According to my readings on ext4 it should allow such big block sized fs. I want to hear your comments. root@ubuntu:~# mkfs.ext4 -b 65536 /dev/sda3 Warning: blocksize 65536 not usable on most systems. mke2fs 1.41.12 (17-May-2010) mkfs.ext4: 65536-byte blocks too big for system (max 4096) Proceed anyway? (y,n) y Warning: 65536-byte blocks too big for system (max 4096), forced to continue Filesystem label= OS type: Linux Block size=65536 (log=6) Fragment size=65536 (log=6) Stride=0 blocks, Stripe width=0 blocks 19968 inodes, 19830 blocks 991 blocks (5.00%) reserved for the super user First data block=0 1 block group 65528 blocks per group, 65528 fragments per group 19968 inodes per group Writing inode tables: done Creating journal (1024 blocks): done Writing superblocks and filesystem accounting information: done This filesystem will be automatically checked every 37 mounts or 180 days, whichever comes first. Use tune2fs -c or -i to override. root@ubuntu:~# tune2fs -l /dev/sda3 tune2fs 1.41.12 (17-May-2010) Filesystem volume name: <none> Last mounted on: <not available> Filesystem UUID: 4cf3f507-e7b4-463c-be11-5b408097099b Filesystem magic number: 0xEF53 Filesystem revision #: 1 (dynamic) Filesystem features: has_journal ext_attr resize_inode dir_index filetype extent flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize Filesystem flags: signed_directory_hash Default mount options: (none) Filesystem state: clean Errors behavior: Continue Filesystem OS type: Linux Inode count: 19968 Block count: 19830 Reserved block count: 991 Free blocks: 18720 Free inodes: 19957 First block: 0 Block size: 65536 Fragment size: 65536 Blocks per group: 65528 Fragments per group: 65528 Inodes per group: 19968 Inode blocks per group: 78 Flex block group size: 16 Filesystem created: Sat Feb 5 14:39:55 2011 Last mount time: n/a Last write time: Sat Feb 5 14:40:02 2011 Mount count: 0 Maximum mount count: 37 Last checked: Sat Feb 5 14:39:55 2011 Check interval: 15552000 (6 months) Next check after: Thu Aug 4 14:39:55 2011 Lifetime writes: 70 MB Reserved blocks uid: 0 (user root) Reserved blocks gid: 0 (group root) First inode: 11 Inode size: 256 Required extra isize: 28 Desired extra isize: 28 Journal inode: 8 Default directory hash: half_md4 Directory Hash Seed: afb5b570-9d47-4786-bad2-4aacb3b73516 Journal backup: inode blocks root@ubuntu:~# mount -t ext4 /dev/sda3 /mnt/ mount: wrong fs type, bad option, bad superblock on /dev/sda3, missing codepage or helper program, or other error In some cases useful info is found in syslog - try dmesg | tail or so

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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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• 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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• 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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• Unable to delete all partitions on flash drive using Windows 7 OS??

  - by irrational John

  Recently I purchased an ADATA C802 8GB flash drive. Since the drive was new I decided to run some of the HD Tune Pro (v4.50) performance tests on it, mostly just for the heck of it. To avoid accidently destroying data HD Tune refuses to write to a drive unless there are no partitions on the drive. If you do attempt to write to a drive with partitions, it posts the message "Writing is disabled. To enable writing please remove all partitions." As you would expect, the ADATA came formatted with a single primary FAT32 partition in the Master Boot Record. But a number of unexpected things happened when I attempted to delete that partition. The first thing I tried was to use the Windows 7 (64-bit) Disk Management tool (diskmgmt.msc) to delete the partition. It would not let me. The context menu choice to delete that volume was not available. Next I opened up a command prompt window with Admin authority and ran diskpart. Diskpart deleted the volume for me. However, when I attempted to run an HD Tune write test on the drive I still got the "Writing is disabled" message. Huh??? So I fired up a utility I have which allows viewing drives at the sector level and verified that the partition table in the Master Boot Record was empty. No partitions. Yet HD Tune still thought there were partitions on the drive? So why was I still getting the "Writing is disabled" message from HD Tune Pro? And why wouldn't the Windows 7 Disk Management tool let me change the partitions on this drive. After doing the above, I plugged the ADATA into my MacBook. I was then able to format it as either a GPT or MBR partitioned drive with no problems. I am not looking for suggestions on how to format this drive. I can do that. What I do not understand and was hoping I might get insight into is why this drive behaves so strangely under Windows 7? And BTW, what's up with HD Tune Pro? BTW, if I plug the drive I formatted on my MacBook back into my Windows 7 64-bit system I still run into road blocks with the Disk Management tool. For example, I cannot delete all the GPT partitions on the ADATA so I can convert it into an MBR drive. I following Microsoft's instructions, the instructions just do not work with this ADATA flash drive. Anyone know what's up with this? It makes no sense to me. Has something changed in Windows 7 (Vista)??

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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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• 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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• Adaptec 5805 not recognized after reboot

  - by Rakedko ShotGuns

  After rebooting the system, the controller is not recognized. It only works if the computer is shut down and turned off. I have recently updated the firmware to "Adaptec RAID 5805 Firmware Build 18948". How do I fix the problem? Configuration summary --------------------------- 1. Server name.....................raid_test Adaptec Storage Manager agent...7.31.00 (18856) Adaptec Storage Manager console.7.31.00 (18856) Number of controllers...........1 Operating system................Windows Configuration information for controller 1 ------------------------------------------------------- Type............................Controller Model...........................Adaptec 5805 Controller number...............1 Physical slot...................2 Installed memory size...........512 MB Serial number...................8C4510C6C9E Boot ROM........................5.2-0 (18948) Firmware........................5.2-0 (18948) Device driver...................5.2-0 (16119) Controller status...............Optimal Battery status..................Charging Battery temperature.............Normal Battery charge amount (%).......37 Estimated charge remaining......0 days, 16 hours, 12 minutes Background consistency check....Disabled Copy back.......................Disabled Controller temperature..........Normal (40C / 104F) Default logical drive task priority High Performance mode................Dynamic Number of logical devices.......1 Number of hot-spare drives......0 Number of ready drives..........0 Number of drive(s) assigned to MaxCache cache0 Maximum drives allowed for MaxCache cache8 MaxCache Read Cache Pool Size...0 GB NCQ status......................Enabled Stay awake status...............Disabled Internal drive spinup limit.....0 External drive spinup limit.....0 Phy 0...........................No device attached Phy 1...........................No device attached Phy 2...........................No device attached Phy 3...........................1.50 Gb/s Phy 4...........................No device attached Phy 5...........................No device attached Phy 6...........................No device attached Phy 7...........................No device attached Statistics version..............2.0 SSD Cache size..................0 Pages on fetch list.............0 Fetch list candidates...........0 Candidate replacements..........0 69319...........................31293 Logical device..................0 Logical device name............. RAID level......................Simple volume Data space......................148,916 GB Date created....................09/19/2012 Interface type..................Serial ATA State...........................Optimal Read-cache mode.................Enabled Preferred MaxCache read cache settingEnabled Actual MaxCache read cache setting Disabled Write-cache mode................Enabled (write-back) Write-cache setting.............Enabled (write-back) Partitioned.....................Yes Protected by hot spare..........No Bootable........................Yes Bad stripes.....................No Power Status....................Disabled Power State.....................Active Reduce RPM timer................Never Power off timer.................Never Verify timer....................Never Segment 0.......................Present: controller 1, connector 0, device 0, S/N 9RX3KZMT Overall host IOs................99075 Overall MB......................4411203 DRAM cache hits.................71929 SSD cache hits..................0 Uncached IOs....................29239 Overall disk failures...........0 DRAM cache full hits............71929 DRAM cache fetch / flush wait...0 DRAM cache hybrid reads.........3476 DRAM cache flushes..............-- Read hits.......................0 Write hits......................0 Valid Pages.....................0 Updates on writes...............0 Invalidations by large writes...0 Invalidations by R/W balance....0 Invalidations by replacement....0 Invalidations by other..........0 Page Fetches....................0 0...............................0 73..............................10822 8...............................3 46138...........................4916 27184...........................15226 20875...........................323 16982...........................1771 1563............................5317 1948............................2969 Serial attached SCSI ----------------------- Type............................Disk drive Vendor..........................Unknown Model...........................ST3160815AS Serial Number...................9RX3KZMT Firmware level..................3.AAD Reported channel................0 Reported SCSI device ID.........0 Interface type..................Serial ATA Size............................149,05 GB Negotiated transfer speed.......1.50 Gb/s State...........................Optimal S.M.A.R.T. error................No Write-cache mode................Write back Hardware errors.................0 Medium errors...................0 Parity errors...................0 Link failures...................0 Aborted commands................0 S.M.A.R.T. warnings.............0 Solid-state disk (non-spinning).false MaxCache cache capable..........false MaxCache cache assigned.........false NCQ status......................Enabled Phy 0...........................1.50 Gb/s Power State.....................Full rpm Supported power states..........Full rpm, Powered off 0x01............................113 0x03............................98 0x04............................99 0x05............................100 0x07............................83 0x09............................75 0x0A............................100 0x0C............................99 0xBB............................100 0xBD............................100 0xBE............................61 0xC2............................39 0xC3............................69 0xC5............................100 0xC6............................100 0xC7............................200 0xC8............................100 0xCA............................100 Aborted commands................0 Link failures...................0 Medium errors...................0 Parity errors...................0 Hardware errors.................0 SMART errors....................0 End of the configuration information for controller 1

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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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• Why doesn't video run smoothly on my laptop anymore?

  - by andygrunt

  This might be an impossible question to answer remotely but I figure there may be some common causes that people can suggest so I think it's worth asking... Video no longer plays smoothly on my laptop. It used to but not for a while now. For example, playing a video on YouTube is pretty typical: I press play (making sure it's not on HD or even HQ) and the video buffers a little then starts to play. At first it plays fine then the video starts to stutter, turning into a slideshow while the sound continues to play smoothly. If I try playing the same video on my Playstation 3 (which is linked to the same network) it plays smoothly so it can't be the connection. Another example is streaming DivX videos. Again, I wait while it buffers and it starts but very soon, instead of a slideshow, this time the video just plays slowly while the sound continues as normal (instantly getting out of sync). Even if I let the video fully load before pressing play (i.e. it's no longer streaming), it still behaves the same way. I can even let it load 100% then save the file to hard disk and use VLC player to view it, and the same thing happens. I'm using an old laptop running Windows XP. For the past several years it's been connected to the router via Wi-Fi but in the past few days I've changed that to a network cable (like my PS3) but that hasn't helped. Yes, I regularly install various bits and pieces of software but nothing that I can identify as being the cause. So, are there known causes of this sort of behaviour and if so, what can I do to fix it? Thanks. Update to answer a few questions... Laptop Spec' (note: video has played back fine for the majority of time I've had the laptop) Toshiba Satellite 1900-603 (possibly called something else outside the UK) Intel Pentium 4 2.2 Ghz Processor Originally had 512Mb memory but recently doubled that to 1 Gig of memory Graphics: ATI Mobility Radeon 16Mb DDR VRAM Windows XP SP3 (Home edition) Over the years I've done several things to speed it up (disabling indexing etc) and am generally happy with the performance. I also regularly have a clear out of old software (if for no other reason than the laptop only has a 40Gb hard disk) and use CCleaner and Glary Utilities to strip out much of the crap from my system. Also recently (after doubling the memory), I've tried a few new things which might be likely candidates for slowing the video down such as Rocketdock, Jingle keyboard (which gives an old style 'clacky' typewriter sound when I type - love it), SugarSync, Taskbar Shuffle. However, the video doesn't play smoothly even when I try quit all these apps.

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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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• 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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• Vista stuck at "Shutting down..." screen. Any way to get verbose logging?

  - by CapBBeard

  Hi all, My home machine has been running fine for about 3 years, no problems at all. Within the last couple of weeks it's had real trouble trying to shut down. It'll get so far and then just sit there at the "Shutting down..." screen for hours. I've left it overnight, I've tried in safe mode, all to no avail. These days, I just wait for the disk activity to finish up and then hold the power button to turn it off. Feels dirty as, especially because there's a RAID involved! The hardware itself is in pretty good shape and of decent spec; Core 2 Quad, 4GB RAM, 1TB RAID 1+0, so it's not quite like a 7 year old PC coming to end of life! In the last month, hardware hasn't changed except for a new monitor. Admittedly I haven't tried unplugging the monitor but I've never heard of that preventing a shutdown. I might give it a whirl later I guess, as a last resort. I've uninstalled old apps, done updates, checked the event log, looked in device manager, uninstalled all non-present devices, disabled various non-critical devices (imaging, audio etc), unplugged peripherals, stopped non-essential services, unplugged the network, disabled the network adapter entirely, ran chkdsk, verified my RAID, the list goes on. But not a single lead. I'm pretty stumped. It could be hardware, but I have no other evidence to suggest so; when the PC is running, it runs fine. Temperatures are good, gaming is smooth as always, disk performance is fine. Event log even makes it look like the shutdown was completed (gets to the point where the event log service stops). In fact, the PC doesn't appear to realise that I cut the power to it. So my question is, does anyone know if there is a way I can get some verbose output (or a log) from shutdown to give me some idea of what is causing the issue? I'm guessing it's stuck unloading some app/driver but it would be good to get some specifics! Unless anyone has any other ideas? I suspect a reinstall would resolve the issue, however I'm looking to get a new PC built in the next month or so, and the reinstall is going to be quite a big job so I'd rather just wait until then if it comes to that. Would still be nice to get this sorted in the mean time though. Cheers!

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• What the best way to achieve RPO of zero and lowest possible RTO (less than 15 minutes) with SQL 2008 R2?

  - by Adrian Hope-Bailie

  We are running a payments (EFT transaction processing) application which is processing high volumes of transactions 24/7 and are currently investigating a better way of doing DB replication to our disaster recovery site. Our current and previous strategies have included using both DoubleTake and Redgate to replicate data to a warm stand-by. DoubleTake is the supported solution from the payments software vendor however their (DoubleTake's) support in South Africa is very poor. We had a few issues and simply couldn't ever resolve them so we had to give up on DoubleTake. We have been using Redgate to manually read the data from the primary site (via queries) and write to the DR site but this is: A bad solution Getting the software vendor hot and bothered whenever we have support issues as it has a tendency to interfere with the payment application which is very DB intensive. We recently upgraded the whole system to run on SQL 2008 R2 Enterprise which means we should probably be looking at using some of the built-in replication features. The server has 2 fairly large databases with a mixture of tables containing highly volatile transactional data and pretty static configuration data. Replication would be done over a WAN link to a separate physical site and needs to achieve the following objectives. RPO: Zero loss - This is transactional data with financial impact so we can't lose anything. RTO: Tending to zero - The business depends on our ability to process transactions every minute we are down we are losing money I have looked at a few of the other questions/answers but none meet our case exactly: SQL Server 2008 failover strategy - Log shipping or replication? How to achieve the following RTO & RPO with logshipping only using SQL Server? What is the best of two approaches to achieve DB Replication? My current thinking is that we should use mirroring but I am concerned that for RPO:0 we will need to do delayed commits and this could impact the performance of the primary DB which is not an option. Our current DR process is to: Stop incoming traffic to the primary site and allow all in-flight transaction to complete. Allow the replication to DR to complete. Change network routing to route to DR site. Start all applications and services on the secondary site (Ideally we can change this to a warmer stand-by whereby the applications are already running but not processing any transactions). In other words the DR database needs to, as quickly as possible, catch up with primary and be ready for processing as the new primary. We would then need to be able to reverse this when we are ready to switch back. Is there a better option than mirroring (should we be doing log-shipping too) and can anyone suggest other considerations that we should keep in mind?

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• Synchronize the same set of files to 2 different locations with 2 different programs for 2 different purposes

  - by Hedgetrimmer

  Because of stupid questionable IT policies at my not-to-be-named place of occupation, I have been (and will be, for the forseeable future) carrying on an external hard drive a unison-synchronized copy of all of my documents and code, including code which resides in some of my "dotfiles" and other code which resides in ~/bin (things I've made are there because ~/bin is in my $PATH) along with some cruft generated (and to be generated) by conscript and its related "giter8" templating system for Scala project boilerplates. Despite this, I do use a symlinking program to store all of my important dotfiles in a subdirectory. Thanks to that somewhat complicated setup, I have resorted to making a directory full of symlinks to every directory (or file, as is the case with stuff under ~/bin) that I want synchronized, and then follow = True is in my unison profile. It happens to be that this collection of odds and ends—plus an automatically-generated text file containing every package installed on my system—is everything under ~ that needs to be backed up to a remote (rsync-over-ssh) host with client-side encryption and signing from GPG. I already believe that duplicity is the most appropriate program to do that. What isn't as clear-cut is how to make duplicity use the exact same set of files when it runs a backup; it would be simple if duplicity would follow symlinks, but it does not and the manpage lists no option for enabling any such behavior. Comparing unison's file selection algorithm to duplicity's, I don't think I can write a program that could compute a ruleset for one program given one for the other. For the record, I would rather not keep the symlinks manually synchronized with duplicity file-selection rules, as they can change thanks to the above-mentioned complications regarding ~/bin. I don't think running duplicity on the external hard disk is such a good idea either; I usually keep that hard disk unmounted and unplugged in case of a power failure or other physical problem with the computer, plus I'm not sure about duplicity's performance given that: the hard disk is NTFS-formatted in order to be useable at my Windows-imprisoned place of occupation. despite being a USB 3.0 disk, my computer has no USB 3.0 ports so it acts as a USB 2.0 disk. How can I have duplicity (or is there a better program that I have overlooked?) back up the exact same set of files that is bidirectionally synchronized with my external hard disk?

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• Is there a Distributed SAN/Storage System out there?

  - by Joel Coel

  Like many other places, we ask our users not to save files to their local machines. Instead, we encourage that they be put on a file server so that others (with appropriate permissions) can use them and that the files are backed up properly. The result of this is that most users have large hard drives that are sitting mainly empty. It's 2010 now. Surely there is a system out there that lets you turn that empty space into a virtual SAN or document library? What I envision is a client program that is pushed out to users' PCs that coordinates with a central server. The server looks to users just like a normal file server, but instead of keeping entire file contents it merely keeps a record of where those files can be found among various user PCs. It then coordinates with the right clients to serve up file requests. The client software would be able to respond to such requests directly, as well as be smart enough to cache recent files locally. For redundancy the server could make sure files are copied to multiple PCs, perhaps allowing you to define groups in different locations so that an instance of the entire repository lives in each group to protect against a disaster in one building taking down everything else. Obviously you wouldn't point your database server here, but for simpler things I see several advantages: Files can often be transferred from a nearer machine. Disk space grows automatically as your company does. Should ultimately be cheaper, as you don't need to keep a separate set of disks I can see a few downsides as well: Occasional degradation of user pc performance, if the machine has to serve or accept a large file transfer during a busy period. Writes have to be propogated around the network several times (though I suspect this isn't really much of a problem, as reading happens in most places more than writing) Still need a way to send a complete copy of the data offsite occasionally, and this would make it very hard to do differentials Think of this like a cloud storage system that lives entirely within your corporate LAN and makes use of your existing user equipment. Our old main file server is due for retirement in about 2 years, and I'm looking into replacing it with a small SAN. I'm thinking something like this would be a better fit. As a school, we have a couple computer labs I can leave running that would be perfect for adding a little extra redundancy to the system. Unfortunately, the closest thing I can find is Dienst, and it's just a paper that dates back to 1994. Am I just using the wrong buzzwords in my searches, or does this really not exist? If not, is there a big downside that I'm missing?

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• Nginx, proxy passing to Apache, and SSL

  - by Vic

  I have Nginx and Apache set up with Nginx proxy-passing everything to Apache except static resources. I have a server set up for port 80 like so: server { listen 80; server_name *.example1.com *.example2.com; [...] location ~* \.(?:ico|css|js|gif|jpe?g|png|pdf|te?xt)$ { access_log off; expires max; add_header Pragma public; add_header Cache-Control "public, must-revalidate, proxy-revalidate"; add_header Vary: Accept-Encoding; } location / { proxy_pass http://127.0.0.1:8080; include /etc/nginx/conf.d/proxy.conf; } } And since we have multiple ssl sites (with different ssl certificates) I have a server{} block for each of them like so: server { listen 443 ssl; server_name *.example1.com; [...] location ~* \.(?:ico|css|js|gif|jpe?g|png|pdf|te?xt)$ { access_log off; expires max; add_header Pragma public; add_header Cache-Control "public, must-revalidate, proxy-revalidate"; add_header Vary: Accept-Encoding; } location / { proxy_pass https://127.0.0.1:8443; include /etc/nginx/conf.d/proxy.conf; proxy_set_header X-Forwarded-Port 443; proxy_set_header X-Forwarded-Proto https; } } server { listen 443 ssl; server_name *.example2.com; [...] location ~* \.(?:ico|css|js|gif|jpe?g|png|pdf|te?xt)$ { access_log off; expires max; add_header Pragma public; add_header Cache-Control "public, must-revalidate, proxy-revalidate"; add_header Vary: Accept-Encoding; } location / { proxy_pass https://127.0.0.1:8445; include /etc/nginx/conf.d/proxy.conf; proxy_set_header X-Forwarded-Port 443; proxy_set_header X-Forwarded-Proto https; } } First of all, I think there is a very obvious problem here, which is that I'm double-encrypting everything, first at the nginx level and then again by Apache. To make everything worse, I just started using Amazon's Elastic Load Balancer, so I added the certificate to the ELB and now SSL encryption is happening three times. That's gotta be horrible for performance. What is the sane way to handle this? Should I be forwarding https on the ELB - http on nginx - http on apache? Secondly, there is so much duplication above. Is the best method to not repeat myself to put all of the static asset handling in an include file and just include it in the server?

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• How to disable or tune filesystem cache sharing for OpenVZ?

  - by gertvdijk

  For OpenVZ, an example of container-based virtualization, it seems that host and all guests are sharing the filesystem cache. This sounds paradoxical when talking about virtualization, but this is actually a feature of OpenVZ. It makes sense too. Because only one kernel is running, it's possible to benefit from sharing the same pages of filesystem cache in memory. And while it sounds beneficial, I think a set up here actually suffers in performance from it. Here's why I think why: my machines aren't actually sharing any files on disk so I can't benefit from this feature in OpenVZ. Several OpenVZ machines are running MySQL with MyISAM tables. MyISAM relies on the system's filesystem cache for caching of data files, unlike InnoDB's buffer pool. Also some virtual machines are known to do heavy and large I/O operations on the same filesystem in the host. For example, when running cat *.MYD > /dev/null on some large database in one machine, I saw the filesystem cache lowering in another, monitored by htop. This essentially flushes all the useful filesystem cache in guests (FIFO) and so it flushes the MySQL caches in the guests. Now users are complaining that MySQL is very slow. And it is. Some simple SELECT queries take several seconds on times disk I/O is heavily used by other machines. So, simply put: Is there a way to avoid filesystem cache being wiped out by other virtual machines in container-based virtualization? Some thoughts: Choosing algorithm for flushing filesystem cache in the kernel. (possible? how?) Reserving a certain amount of pages for a single VM. (seems no option for filesystem cache type of pages that reading man vzctl) Will running MySQL on another filesystem get me anywhere? If not, I think my alternatives are: Use KVM for MySQL-MyISAM running VMs. KVM actually assigns memory to the VM and does not allow swapping out caches unless using a balloon driver. Move to InnoDB and tune the buffer pools, dirty pages, etc. This is now considered to be 'nice to have' on the long-term as not everyone responsible for administration of the system understands InnoDB. more suggestions welcome. System software: Proxmox (now 1.9, could be upgraded to 2.x). One big LV assigned for the VMs.

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• Add Machine Key to machine.config in Load Balancing environment to multiple versions of .net framework

  - by davidb

  I have two web servers behind a F5 load balancer. Each web server has identical applications to the other. There was no issue until the config of the load balancer changed from source address persistence to least connections. Now in some applications I receieve this error Server Error in '/' Application. Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.Web.HttpException: Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster. Source Error: The source code that generated this unhandled exception can only be shown when compiled in debug mode. To enable this, please follow one of the below steps, then request the URL: Add a "Debug=true" directive at the top of the file that generated the error. Example: or: 2) Add the following section to the configuration file of your application: Note that this second technique will cause all files within a given application to be compiled in debug mode. The first technique will cause only that particular file to be compiled in debug mode. Important: Running applications in debug mode does incur a memory/performance overhead. You should make sure that an application has debugging disabled before deploying into production scenario. How do I add a machine key to the machine.config file? Do I do it at server level in IIS or at website/application level for each site? Does the validation and decryption keys have to be the same across both web servers or are they different? Should they be different for each machine.config version of .net? I cannot find any documentation of this scenario.

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• Will spreading your servers load not just consume more recourses

  - by Saif Bechan

  I am running a heavy real-time updating website. The amount of recourses needed per user are quite high, ill give you an example. Setup Every visit The application is php/mysql so on every visit static and dynamic content is loaded. Recourses: apache,php,mysql Every second (no more than a second will just be too long) The website needs to be updated real-time so every second there is an ajax call thats updates the website. Recourses: jQuery,apache,php,mysql Avarage spending for single user (spending one minute and visited 3 pages) Apache: +/- 63 requests / responsess serving static and dynamic content (img,css,js,html) php: +/- 63 requests / responses mysql: +/- 63 requests / responses jquery: +/- 60 requests / responses Optimization I want to optimize this process, but I think that maybe it would be just the same in the end. Before implementing and testing (which will take weeks) I wanted to have some second opinions from you guys. Every visit I want to start off with having nginx in the front and work as a proxy to deliver the static content. Recources: Dynamic: apache,php,mysql Static: nginx This will spread the load on apache a lot. Every Second For the script that loads every second I want to set up Node.js server side javascript with nginx in te front. I want to set it up that jquery makes a request ones a minute, and node.js streams the data to the client every second. Recources: jQuery,nginx,node.js,mysql Avarage spending for single user (spending one minute and visited 3 pages) Nginx: 4 requests / responsess serving mostly static conetent(img,css,js) Apache: 3 requests only the pages php: 3 requests only the pages node.js: 1 request / 60 responses jquery: 1 request / 60 responses mysql: 63 requests / responses Optimization As you can see in the optimisation the load from Apache and PHP are lifted and places on nginx and node.js. These are known for there light footprint and good performance. But I am having my doubts, because there are still 2 programs extra loaded in the memory and they consume cpu. So it it better to have less programs that do the job, or more. Before I am going to spend a lot of time setting this up I would like to know if it will be worth the while.

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• nginx rewrite for /blah/(.*) /$1

  - by skrewler

  I'm migrating from mod_php to nginx. I got everything working except for this rewrite.. I'm just not familiar enough with nginx configuration to know the correct way to do this. I came up with this by looking at a sample on the nginx site. server { server_name test01.www.myhost.com; root /home/vhosts/my_home/blah; access_log /var/log/nginx/blah.access.log; error_log /var/log/nginx/blah.error.log; index index.php; location / { try_files $uri $uri/ @rewrites; } location @rewrites { rewrite ^ /index.php last; rewrite ^/ht/userGreeting.php /js/iFrame/index.php last; rewrite ^/ht/(.*)$ /$1 last; rewrite ^/userGreeting.php$ /js/iFrame/index.php last; rewrite ^/a$ /adminLogin.php last; rewrite ^/boom\/(.*)$ /boom/index.php?q=$1 last; rewrite ^favicon.ico$ favico_ry.ico last; } # This block will catch static file requests, such as images, css, js # The ?: prefix is a 'non-capturing' mark, meaning we do not require # the pattern to be captured into $1 which should help improve performance location ~* \.(?:ico|css|js|gif|jpe?g|png)$ { # Some basic cache-control for static files to be sent to the browser expires max; add_header Pragma public; add_header Cache-Control "public, must-revalidate, proxy-revalidate"; } include php.conf; } The issue I'm having is with this rewrite: rewrite ^ht\/(.*)$ /$1 last; 99% of requests that will hit this rewrite are static files. So I think maybe it's getting sent to the static files section and that's where things are being messed up? I tried adding this but it didn't work: location ~* ^ht\/.*\.(?:ico|css|js|gif|jpe?g|png)$ { # Some basic cache-control for static files to be sent to the browser expires max; add_header Pragma public; add_header Cache-Control "public, must-revalidate, proxy-revalidate"; } Any help would be appreciated. I know the best thing to do would be to just change the references of /ht/whatever.jpg to /whatever.jpg in the code.. but that's not an option for now.

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• MongoDB and datasets that don't fit in RAM no matter how hard you shove

  - by sysadmin1138

  This is very system dependent, but chances are near certain we'll scale past some arbitrary cliff and get into Real Trouble. I'm curious what kind of rules-of-thumb exist for a good RAM to Disk-space ratio. We're planning our next round of systems, and need to make some choices regarding RAM, SSDs, and how much of each the new nodes will get. But now for some performance details! During normal workflow of a single project-run, MongoDB is hit with a very high percentage of writes (70-80%). Once the second stage of the processing pipeline hits, it's extremely high read as it needs to deduplicate records identified in the first half of processing. This is the workflow for which "keep your working set in RAM" is made for, and we're designing around that assumption. The entire dataset is continually hit with random queries from end-user derived sources; though the frequency is irregular, the size is usually pretty small (groups of 10 documents). Since this is user-facing, the replies need to be under the "bored-now" threshold of 3 seconds. This access pattern is much less likely to be in cache, so will be very likely to incur disk hits. A secondary processing workflow is high read of previous processing runs that may be days, weeks, or even months old, and is run infrequently but still needs to be zippy. Up to 100% of the documents in the previous processing run will be accessed. No amount of cache-warming can help with this, I suspect. Finished document sizes vary widely, but the median size is about 8K. The high-read portion of the normal project processing strongly suggests the use of Replicas to help distribute the Read traffic. I have read elsewhere that a 1:10 RAM-GB to HD-GB is a good rule-of-thumb for slow disks, As we are seriously considering using much faster SSDs, I'd like to know if there is a similar rule of thumb for fast disks. I know we're using Mongo in a way where cache-everything really isn't going to fly, which is why I'm looking at ways to engineer a system that can survive such usage. The entire dataset will likely be most of a TB within half a year and keep growing.

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• What DNS server to use for dynamic load-balancing of website?

  - by Marki555

  I will have 2 servers in different datacenters (different countries) and I want to use DNS load-balancing mainly for High Availability of website hosted on those 2 servers. It is just ad tracking site, which records hit in local database and returns few lines on html code. I want to return 2 A records each time because of DNS pinning in browsers (if one server fails, browser will try second A record which it has already cached). Both servers will be acting also as DNS servers for redundancy. Now comes my proposed solution: I will use BIND and have both servers as a master for that zone. On each server there will be running script, which will periodically test availability (http) of both servers and remove IP from DNS in case of failure. Now the questions :) 1) Is BIND suitable for this solution? I think BIND performance is good and it is easy to manipulate the zone file via script. And as I will modify the zone only in case of failure/maintenance, the modifications (and thus bind reload) won't be often. 2) I plan to use TTL of 5 minutes. The website will have about 1000-3000 req/s but from distinct clients (each IP only 1-3 requests), so I think the DNS load won't be too much. I suppose their ISPs will cache the responses for those 5 mins. Is there any reason to lower the TTL even more? 3) Is my master-master approach good? Or should I make one of the servers master and the other one slave? Right now each server can monitor both itself and the other one. If only webservice fails, both DNS nodes will notice it. If the whole server fails, then the remaining DNS node will notice it and the failed node will not answer DNS queries anyway. 4) Is it a big issue when one NS server does not respond to queries? If yes, I can make a third DNS, so anytime at least 2 of them would accept queries... 5) Should I rewrite the zone file via script, or just use dynamic DNS update (for example via nsupdateutility)?

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• Troubleshooting Network Speeds -- The Age Old Inquiry

  - by John K

  I'm looking for help with what I'm sure is an age old question. I've found myself in a situation of yearning to understand network throughput more clearly, but I can't seem to find information that makes it "click" We have a few servers distributed geographically, running various versions of Windows. Assuming we always use one host (a desktop) as the source, when copying data from that host to other servers across the country, we see a high variance in speed. In some cases, we can copy data at 12MB/s consistently, in others, we're seeing 0.8 MB/s. It should be noted, after testing 8 destinations, we always seem to be at either 0.6-0.8MB/s or 11-12 MB/s. In the building we're primarily concerned with, we have an OC-3 connection to our ISP. I know there are a lot of variables at play, but I guess I was hoping the experts here could help answer a few basic questions to help bolster my understanding. 1.) For older machines, running Windows XP, server 2003, etc, with a 100Mbps Ethernet card and 72 ms typical latency, does 0.8 MB/s sound at all reasonable? Or do you think that slow enough to indicate a problem? 2.) The classic "mathematical fastest speed" of "throughput = TCP window / latency," is, in our case, calculated to 0.8 MB/s (64Kb / 72 ms). My understanding is that is an upper bounds; that you would never expect to reach (due to overhead) let alone surpass that speed. In some cases though, we're seeing speeds of 12.3 MB/s. There are Steelhead accelerators scattered around the network, could those account for such a higher transfer rate? 3.) It's been suggested that the use SMB vs. SMB2 could explain the differences in speed. Indeed, as expected, packet captures show both being used depending on the OS versions in play, as we would expect. I understand what determines SMB2 being used or not, but I'm curious to know what kind of performance gain you can expect with SMB2. My problem simply seems to be a lack of experience, and more importantly, perspective, in terms of what are and are not reasonable network speeds. Could anyone help impart come context/perspective?

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• How to prevent dual booted OSes from damaging each other?

  - by user1252434

  For better compatibility and performance in games I'm thinking about installing Windows additionally to Linux. I have security concerns about this, though. Note: "Windows" in the remaining text includes not only the OS but also any software running on it. Regardless of whether it comes included or is additionally installed, whether it is started intentionally or unintentionally (virus, malware). Is there an easy way to achieve the following requirements: Windows MUST NOT be able to kill my linux partition or my data disk neither single files (virus infection) nor overwriting the whole disk Windows MUST NOT be able to read data disk (- extra protection against spyware) Linux may or may not have access to the windows partition both Linux and Windows should have full access to the graphics card this rules out desktop VM solutions for gaming I want the manufacturer's windows graphics card driver Regarding Windows to be unable to destroy my linux install: this is not just the usual paranoia, that has happened to me in the past. So I don't accept "no ext4 driver" as an argument. Once bitten, twice shy. And even if destruction targeted at specific (linux) files is nearly impossible, there should be no way to shred the whole partition. I may accept the risk of malware breaking out of a barrier (e.g. VM) around the whole windows box, though. Currently I have a system disk (SSD) and a data disk (HDD), both SATA. I expect I have to add another disk. If i don't: even better. My CPU is a Intel Core i5, with VT-x and VT-d available, though untested. Ideas I've had so far: deactivate or hide other HDs until reboot at low level possible? can the boot loader (grub) do this for me? tiny VM layer: load windows in a VM that provides access to almost all hardware, except the HDs any ready made software solution for this? Preferably free. as I said: the main problem seems to be to provide full access to the graphics card hardware switch to cut power to disks commercial products expensive and lots of warnings against cheap home built solutions preferably all three hard disks with one switch (one push) mobile racks - won't wear of daily swapping be a problem?

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