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• Why does my dd backup of MacBook OS X fail to boot upon restore?

  - by James

  I created a backup of a MacBook hard drive (WD2500BEVS-88US) by hooking it up as a secondary drive on my linux system (Ubuntu 10.10). I used the following command: sudo dd if=/dev/sdc of=/home/backup.img bs=2M This appears to have completed with no errors. I noticed that the file is only 68 GB in size even though the drive is 250 GB in capacity. I restored the image to a spare drive (WD2500BEVS) with the following command: sudo dd if=/home/backup.img of=/dev/sdb bs=2M When I boot the spare drive in the Mac, it appears to start up for a few seconds and then shuts down. (It does not appear to load into the OS at all). When I open up the drive that won't boot in GParted, it looks like this: When looking at the information for the middle partition with the little red exclamation mark, it shows this: The original hard drive that boots ok shows up like this: Further info on both drives: sudo fdisk -l Disk /dev/sdb: 250.1 GB, 250059350016 bytes 255 heads, 63 sectors/track, 30401 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Device Boot Start End Blocks Id System /dev/sdb1 1 30402 244198580 ee GPT WARNING: GPT (GUID Partition Table) detected on '/dev/sdc'! The util fdisk doesn't support GPT. Use GNU Parted. Disk /dev/sdc: 250.1 GB, 250059350016 bytes 255 heads, 63 sectors/track, 30401 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Device Boot Start End Blocks Id System /dev/sdc1 1 30402 244198580 ee GPT So why is my backup or restore failing? Why is dd not creating a byte for byte duplicate?

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• Openfiler iSCSI performance

  - by Justin

  Hoping someone can point me in the right direction with some iSCSI performance issues I'm having. I'm running Openfiler 2.99 on an older ProLiant DL360 G5. Dual Xeon processor, 6GB ECC RAM, Intel Gigabit Server NIC, SAS controller with and 3 10K SAS drives in a RAID 5. When I run a simple write test from the box directly the performance is very good: [root@localhost ~]# dd if=/dev/zero of=tmpfile bs=1M count=1000 1000+0 records in 1000+0 records out 1048576000 bytes (1.0 GB) copied, 4.64468 s, 226 MB/s So I created a LUN, attached it to another box I have running ESXi 5.1 (Core i7 2600k, 16GB RAM, Intel Gigabit Server NIC) and created a new datastore. Once I created the datastore I was able to create and start a VM running CentOS with 2GB of RAM and 16GB of disk space. The OS installed fine and I'm able to use it but when I ran the same test inside the VM I get dramatically different results: [root@localhost ~]# dd if=/dev/zero of=tmpfile bs=1M count=1000 1000+0 records in 1000+0 records out 1048576000 bytes (1.0 GB) copied, 26.8786 s, 39.0 MB/s [root@localhost ~]# Both servers have brand new Intel Server NIC's and I have Jumbo Frames enabled on the switch, the openfiler box as well as the VMKernel adapter on the ESXi box. I can confirm this is set up properly by using the vmkping command from the ESXi host: ~ # vmkping 10.0.0.1 -s 9000 PING 10.0.0.1 (10.0.0.1): 9000 data bytes 9008 bytes from 10.0.0.1: icmp_seq=0 ttl=64 time=0.533 ms 9008 bytes from 10.0.0.1: icmp_seq=1 ttl=64 time=0.736 ms 9008 bytes from 10.0.0.1: icmp_seq=2 ttl=64 time=0.570 ms The only thing I haven't tried as far as networking goes is bonding two interfaces together. I'm open to trying that down the road but for now I am trying to keep things simple. I know this is a pretty modest setup and I'm not expecting top notch performance but I would like to see 90-100MB/s. Any ideas?

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• Dell PE2950 - slow IO rates for writing and reading locally

  - by OrenM

  I'm having a serious issue with dell server PE2950. The server has really slow IO rates, so slow that I'm not able to use it anymore I tried few things to solve this: changing disks to new disks (configured them as raid1) changing perc card + perc cables reinstalling the OS of course, had to cause of changing of disks, centos 5.5 x64bit firmware update to everything virtual disks policy: No Read Ahead,Write Back, disk cache policy disabled. openmanage doesn't alert about anything, also i ran dell's diag tests, everything passed, also dell didn't see anything in deset log. dell offered to reseat everything, including the cpu, we did that as well, still io rates are slow I have several PE2950 servers, and I never had such a thing with any of those. All have similar or exact hardware as this one, all configured the same, with the same os centos 5.5 x64, same disks, same raid, same policy. Just for comparison: the problematic PE2950 server: [root@bad ~]# time sh -c "dd if=/dev/zero of=/tmp/ddfile bs=8k count=200000 && sync" 200000+0 records in 200000+0 records out 1638400000 bytes (1.6 GB) copied, 27.7946 seconds, 58.9 MB/s real 0m33.968s user 0m0.531s sys 0m26.000s good PE2950 server (with the exact same hardware): [root@good ~]# time sh -c "dd if=/dev/zero of=/tmp/ddfile bs=8k count=200000 && sync" 200000+0 records in 200000+0 records out 1638400000 bytes (1.6 GB) copied, 3.19999 seconds, 512 MB/s real 0m7.694s user 0m0.053s sys 0m4.057s Hopefully you will have an idea what can cause the problem.

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• needing storage integrity (write/read) test - for BASH

  - by Mr. Bash

  In need of shell scripts / bash commands to verify data integrity of local harddrives, usb-drives, etc, ... Like the famous www.heise.de/download/h2testw; or something that is at least common within repositories. (h2testw writes a specific datastring over and over onto the medium, then reads it again to verify if it was written correctly and displays write/read time/speed.) please no dd if=/dev/random of=/dev/sdx bs=1k && dd if=/dev/sdx of=/dev/null bs=1k since it won't verify if everything was written correctly. It is only a test if read/write is successful to the device. So far, I'm not too happy with badblocks -w -v /dev/sdx1 either, since it seems rather slow and I don't know what it exactly writes, and if it considers wear-leveling on flash media. There is also a program named F3 http://oss.digirati.com.br/f3/ that needs to be compiled. Designed after h2testw, the concept sounds interesting, i'd just rather have it as a ready to go bash script.

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• Network latency and speed of light

  - by James

  This was kinda of covered by the following Is minimum latency fixed by the speed of light? , but i would like to add the follow up a bit. The scenario is as follows; we have two opposing sites one on the West Coast of the US and one in Ireland. The customer is in central Europe, and has requested a latency test. Ireland gives responses of ~65-70ms. However the West Coast guys claim to be faster with a response of 60ms. Now a quick check says that light in fiber would take about 42ms to make the trip to the States and 8.5ms to Ireland. So obviously this is a single hop and does not include routers, switches, firewalls, protocol overhead etc. Would I be right to call BS on their figures? As a final note I tested a ping to Google IP address that was allegedly on the west coast from a site that covered a similar distance and was amazed to get a response time of 20ms. Suggesting ICMP packets that travel twice the speed of light. So A) what am I missing B) Am I right to suspect shenanigans? UPDATE: Guys thanks so far for your help and I have been reading various previous questions on this. About 5 years I had an issue where the hop from the UK to Ireland added 10ms of latency no matter what we did. In the end I moved the servers; So imagine my surprise when I have guys that claim they are 5ms faster with a transatlantic trip. So again should I call BS? Oh and assume both sites are normal mortals that don't have access to Google magical routing, warp dives or flux capacitors. :)

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• How do I create an MBR on a USB stick using DD command line tool

  - by Lana Miller

  Okay I'm trying to create a BOOTABLE Windows7 image on a USB key from a Mac running Lion. My image is .iso format. I tried: sudo dd if=/Users/myusername/Win7.iso of=/dev/disk1 bs=1m And this succeeded in writing the files, except in DISK UTILITY on the mac, it shows the partition type as GUID Partition Table and not 'Master Boor Record'. Booting the key on my Vista computer yields the error "No boot sector on USB Device' From what I can tell, bs=1m in the DD command should have left 1 Megabyte for the boot sector, but for some reason this area of the USB Key is not set up correctly so that it will boot How can I fix this, or correctly use dd to write a bootable cd image such that it is now a bootable usb drive? Note: in the instructions I read about, they recommended renaming my Win7.iso to Win7.dmg before using DD, which made absolutely no sense to me, so I didn't do it. I could try with that step now, but it takes 1.99 hours to write the image to the USB drive so there is a huge penalty to trial and error here. Thank you.

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• Why dd finishes instantly when pipelining to cat?

  - by agsamek

  I start bash on Cygwin and type: dd if=/dev/zero | cat /dev/null It finishes instantly. When I type: dd if=/dev/zero > /dev/null it runs as expected and I can issue killall -USR1 dd to see the progress. Why does the former invocation finishes instantly? Is it the same on a Linux box? * Explanation why I asked such stupid question and possibly not so stupid question I was compressing hdd images and some were compressed incorrectly. I ended up with the following script showing the problem: while sleep 1 ; do killall -v -USR1 dd ; done & dd if=/dev/zero bs=5000000 count=200 | gzip -c | gzip -cd | wc -c Wc should write 1000000000 at the end. The problem is that it does not on my machine: bash-3.2$ dd if=/dev/zero bs=5000000 count=200 | gzip -c | gzip -cd | wc -c 13+0 records in 12+0 records out 60000000 bytes (60 MB) copied, 0.834 s, 71.9 MB/s 27+0 records in 26+0 records out 130000000 bytes (130 MB) copied, 1.822 s, 71.4 MB/s 200+0 records in 200+0 records out 1000000000 bytes (1.0 GB) copied, 13.231 s, 75.6 MB/s 1005856128 Is it a bug or am I doing something wrong once again?

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• Howto setup neocomplcache?

  - by eddy

  I just started using vim and saw a cool plugin: [neocomplcache].(http://www.vim.org/scripts/script.php?script_id=2620) My Problem is, that I can't get it to work properly. After installing, I took the example config from the help files of neocomplcache and added the lines to my .vimrc At first I wanted to create a simple latex file (there are snippets for tex). After typing "begi" there appears a menu, I can choose between the snippets with TAB or <C-n>. But how do I get them to expand? <C-k> does not work, but I don't understand why. ======== .vimrc: ======== .... " Plugin key-mappings. imap <C-k> <Plug>(neocomplcache_snippets_expand) smap <C-k> <Plug>(neocomplcache_snippets_expand) inoremap <expr><C-g> neocomplcache#undo_completion() inoremap <expr><C-l> neocomplcache#complete_common_string() " Recommended key-mappings. " <CR>: close popup and save indent. inoremap <expr><CR> neocomplcache#smart_close_popup() ."\<CR>" " <TAB>: completion. inoremap <expr><TAB> pumvisible() ? "\<C-n>" : "\<TAB>" " <C-h>, <BS>: close popup and delete backword char. inoremap <expr><C-h> neocomplcache#smart_close_popup()."\<C-h>" inoremap <expr><BS> neocomplcache#smart_close_popup()."\<C-h>" inoremap <expr><C-y> neocomplcache#close_popup() inoremap <expr><C-e> neocomplcache#cancel_popup() ...

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• OpenVPN access to a private network

  - by Gior312

  There are many similar topics about my issue, however I cannot figure out a solution for myself. There are three hosts. A without a routable address but with an Internet access. Server S with a routable Internet address and host B behind NAT in a private network. What I've managed to do is a OpenVPN connection between A and B via S. Everything works fine so far according to this manual VPN Setup What I want to do is to connect A to Bs private network 10.A.B.x I tried this manual but had no luck. So A has a vpn address 10.9.0.10, B's vpn address is 10.9.0.6 and B's private network is 10.20.20.0/24. When at the Server I try to make a route to Bs private network like this sudo route add 10.20.20.0 netmask 255.255.255.0 gw 10.9.0.6 dev tun0 it says "route: netmask 000000ff doesn't make sense with host route" but I don't know how to tell Server to look for a private network in a different way. Do you know how can I make it right ?

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• Why is my rsync so slow?

  - by iblue

  My Laptop and my workstation are both connected to a Gigabit Switch. Both are running Linux. But when I copy files with rsync, it performs badly. I get about 22 MB/s. Shouldn't I theoretically get about 125 MB/s? What is the limiting factor here? EDIT: I conducted some experiments. Write performance on the laptop The laptop has a xfs filesystem with full disk encryption. It uses aes-cbc-essiv:sha256 cipher mode with 256 bits key length. Disk write performance is 58.8 MB/s. iblue@nerdpol:~$ LANG=C dd if=/dev/zero of=test.img bs=1M count=1024 1073741824 Bytes (1.1 GB) copied, 18.2735 s, 58.8 MB/s Read performance on the workstation The files I copied are on a software RAID-5 over 5 HDDs. On top of the raid is a lvm. The volume itself is encrypted with the same cipher. The workstation has a FX-8150 cpu that has a native AES-NI instruction set which speeds up encryption. Disk read performance is 256 MB/s (cache was cold). iblue@raven:/mnt/bytemachine/imgs$ dd if=backup-1333796266.tar.bz2 of=/dev/null bs=1M 10213172008 bytes (10 GB) copied, 39.8882 s, 256 MB/s Network performance I ran iperf between the two clients. Network performance is 939 Mbit/s iblue@raven $ iperf -c 94.135.XXX ------------------------------------------------------------ Client connecting to 94.135.XXX, TCP port 5001 TCP window size: 23.2 KByte (default) ------------------------------------------------------------ [ 3] local 94.135.XXX port 59385 connected with 94.135.YYY port 5001 [ ID] Interval Transfer Bandwidth [ 3] 0.0-10.0 sec 1.09 GBytes 939 Mbits/sec

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• Various problems with software raid1 array built with Samsung 840 Pro SSDs

  - by Andy B

  I am bringing to ServerFault a problem that is tormenting me for 6+ months. I have a CentOS 6 (64bit) server with an md software raid-1 array with 2 x Samsung 840 Pro SSDs (512GB). Problems: Serious write speed problems: root [~]# time dd if=arch.tar.gz of=test4 bs=2M oflag=sync 146+1 records in 146+1 records out 307191761 bytes (307 MB) copied, 23.6788 s, 13.0 MB/s real 0m23.680s user 0m0.000s sys 0m0.932s When doing the above (or any other larger copy) the load spikes to unbelievable values (even over 100) going up from ~ 1. When doing the above I've also noticed very weird iostat results: Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util sda 0.00 1589.50 0.00 54.00 0.00 13148.00 243.48 0.60 11.17 0.46 2.50 sdb 0.00 1627.50 0.00 16.50 0.00 9524.00 577.21 144.25 1439.33 60.61 100.00 md1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 md2 0.00 0.00 0.00 1602.00 0.00 12816.00 8.00 0.00 0.00 0.00 0.00 md0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 And it keeps it this way until it actually writes the file to the device (out from swap/cache/memory). The problem is that the second SSD in the array has svctm and await roughly 100 times larger than the second. For some reason the wear is different between the 2 members of the array root [~]# smartctl --attributes /dev/sda | grep -i wear 177 Wear_Leveling_Count 0x0013 094% 094 000 Pre-fail Always - 180 root [~]# smartctl --attributes /dev/sdb | grep -i wear 177 Wear_Leveling_Count 0x0013 070% 070 000 Pre-fail Always - 1005 The first SSD has a wear of 6% while the second SSD has a wear of 30%!! It's like the second SSD in the array works at least 5 times as hard as the first one as proven by the first iteration of iostat (the averages since reboot): Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util sda 10.44 51.06 790.39 125.41 8803.98 1633.11 11.40 0.33 0.37 0.06 5.64 sdb 9.53 58.35 322.37 118.11 4835.59 1633.11 14.69 0.33 0.76 0.29 12.97 md1 0.00 0.00 1.88 1.33 15.07 10.68 8.00 0.00 0.00 0.00 0.00 md2 0.00 0.00 1109.02 173.12 10881.59 1620.39 9.75 0.00 0.00 0.00 0.00 md0 0.00 0.00 0.41 0.01 3.10 0.02 7.42 0.00 0.00 0.00 0.00 What I've tried: I've updated the firmware to DXM05B0Q (following reports of dramatic improvements for 840Ps after this update). I have looked for "hard resetting link" in dmesg to check for cable/backplane issues but nothing. I have checked the alignment and I believe they are aligned correctly (1MB boundary, listing below) I have checked /proc/mdstat and the array is Optimal (second listing below). root [~]# fdisk -ul /dev/sda Disk /dev/sda: 512.1 GB, 512110190592 bytes 255 heads, 63 sectors/track, 62260 cylinders, total 1000215216 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00026d59 Device Boot Start End Blocks Id System /dev/sda1 2048 4196351 2097152 fd Linux raid autodetect Partition 1 does not end on cylinder boundary. /dev/sda2 * 4196352 4605951 204800 fd Linux raid autodetect Partition 2 does not end on cylinder boundary. /dev/sda3 4605952 814106623 404750336 fd Linux raid autodetect root [~]# fdisk -ul /dev/sdb Disk /dev/sdb: 512.1 GB, 512110190592 bytes 255 heads, 63 sectors/track, 62260 cylinders, total 1000215216 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x0003dede Device Boot Start End Blocks Id System /dev/sdb1 2048 4196351 2097152 fd Linux raid autodetect Partition 1 does not end on cylinder boundary. /dev/sdb2 * 4196352 4605951 204800 fd Linux raid autodetect Partition 2 does not end on cylinder boundary. /dev/sdb3 4605952 814106623 404750336 fd Linux raid autodetect /proc/mdstat root # cat /proc/mdstat Personalities : [raid1] md0 : active raid1 sdb2[1] sda2[0] 204736 blocks super 1.0 [2/2] [UU] md2 : active raid1 sdb3[1] sda3[0] 404750144 blocks super 1.0 [2/2] [UU] md1 : active raid1 sdb1[1] sda1[0] 2096064 blocks super 1.1 [2/2] [UU] unused devices: Running a read test with hdparm root [~]# hdparm -t /dev/sda /dev/sda: Timing buffered disk reads: 664 MB in 3.00 seconds = 221.33 MB/sec root [~]# hdparm -t /dev/sdb /dev/sdb: Timing buffered disk reads: 288 MB in 3.01 seconds = 95.77 MB/sec But look what happens if I add --direct root [~]# hdparm --direct -t /dev/sda /dev/sda: Timing O_DIRECT disk reads: 788 MB in 3.01 seconds = 262.08 MB/sec root [~]# hdparm --direct -t /dev/sdb /dev/sdb: Timing O_DIRECT disk reads: 534 MB in 3.02 seconds = 176.90 MB/sec Both tests increase but /dev/sdb doubles while /dev/sda increases maybe 20%. I just don't know what to make of this. As suggested by Mr. Wagner I've done another read test with dd this time and it confirms the hdparm test: root [/home2]# dd if=/dev/sda of=/dev/null bs=1G count=10 10+0 records in 10+0 records out 10737418240 bytes (11 GB) copied, 38.0855 s, 282 MB/s root [/home2]# dd if=/dev/sdb of=/dev/null bs=1G count=10 10+0 records in 10+0 records out 10737418240 bytes (11 GB) copied, 115.24 s, 93.2 MB/s So sda is 3 times faster than sdb. Or maybe sdb is doing also something else besides what sda does. Is there some way to find out if sdb is doing more than what sda does? UPDATE Again, as suggested by Mr. Wagner, I have swapped the 2 SSDs. And as he thought it would happen, the problem moved from sdb to sda. So I guess I'll RMA one of the SSDs. I wonder if the cage might be problematic. What is wrong with this array? Please help!

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• Why would Linux VM in vSphere ESXi 5.5 show dramatically increased disk i/o latency?

  - by mhucka

  I'm stumped and I hope someone else will recognize the symptoms of this problem. Hardware: new Dell T110 II, dual-core Pentium G860 2.9 GHz, onboard SATA controller, one new 500 GB 7200 RPM cabled hard drive inside the box, other drives inside but not mounted yet. No RAID. Software: fresh CentOS 6.5 virtual machine under VMware ESXi 5.5.0 (build 174 + vSphere Client). 2.5 GB RAM allocated. The disk is how CentOS offered to set it up, namely as a volume inside an LVM Volume Group, except that I skipped having a separate /home and simply have / and /boot. CentOS is patched up, ESXi patched up, latest VMware tools installed in the VM. No users on the system, no services running, no files on the disk but the OS installation. I'm interacting with the VM via the VM virtual console in vSphere Client. Before going further, I wanted to check that I configured things more or less reasonably. I ran the following command as root in a shell on the VM: for i in 1 2 3 4 5 6 7 8 9 10; do dd if=/dev/zero of=/test.img bs=8k count=256k conv=fdatasync done I.e., just repeat the dd command 10 times, which results in printing the transfer rate each time. The results are disturbing. It starts off well: 262144+0 records in 262144+0 records out 2147483648 bytes (2.1 GB) copied, 20.451 s, 105 MB/s 262144+0 records in 262144+0 records out 2147483648 bytes (2.1 GB) copied, 20.4202 s, 105 MB/s ... but after 7-8 of these, it then prints 262144+0 records in 262144+0 records out 2147483648 bytes (2.1 GG) copied, 82.9779 s, 25.9 MB/s 262144+0 records in 262144+0 records out 2147483648 bytes (2.1 GB) copied, 84.0396 s, 25.6 MB/s 262144+0 records in 262144+0 records out 2147483648 bytes (2.1 GB) copied, 103.42 s, 20.8 MB/s If I wait a significant amount of time, say 30-45 minutes, and run it again, it again goes back to 105 MB/s, and after several rounds (sometimes a few, sometimes 10+), it drops to ~20-25 MB/s again. Plotting the disk latency in vSphere's interface, it shows periods of high disk latency hitting 1.2-1.5 seconds during the times that dd reports the low throughput. (And yes, things get pretty unresponsive while that's happening.) What could be causing this? I'm comfortable that it is not due to the disk failing, because I also had configured two other disks as an additional volume in the same system. At first I thought I did something wrong with that volume, but after commenting the volume out from /etc/fstab and rebooting, and trying the tests on / as shown above, it became clear that the problem is elsewhere. It is probably an ESXi configuration problem, but I'm not very experienced with ESXi. It's probably something stupid, but after trying to figure this out for many hours over multiple days, I can't find the problem, so I hope someone can point me in the right direction. (P.S.: yes, I know this hardware combo won't win any speed awards as a server, and I have reasons for using this low-end hardware and running a single VM, but I think that's besides the point for this question [unless it's actually a hardware problem].) ADDENDUM #1: Reading other answers such as this one made me try adding oflag=direct to dd. However, it makes no difference in the pattern of results: initially the numbers are higher for many rounds, then they drop to 20-25 MB/s. (The initial absolute numbers are in the 50 MB/s range.) ADDENDUM #2: Adding sync ; echo 3 > /proc/sys/vm/drop_caches into the loop does not make a difference at all. ADDENDUM #3: To take out further variables, I now run dd such that the file it creates is larger than the amount of RAM on the system. The new command is dd if=/dev/zero of=/test.img bs=16k count=256k conv=fdatasync oflag=direct. Initial throughput numbers with this version of the command are ~50 MB/s. They drop to 20-25 MB/s when things go south. ADDENDUM #4: Here is the output of iostat -d -m -x 1 running in another terminal window while performance is "good" and then again when it's "bad". (While this is going on, I'm running dd if=/dev/zero of=/test.img bs=16k count=256k conv=fdatasync oflag=direct.) First, when things are "good", it shows this: When things go "bad", iostat -d -m -x 1 shows this:

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• SqlDataAdapter Update is not working in C# wih Sql Server

  - by Ahmed

  I am trying to save data from C# form to Sql server Northwind Orders database, I am only using CustomerID, OrderDate and ShippedDate for data entry. Following is the code to Form load and save button: private void Form1_Load(object sender, EventArgs e) { SetComb(); connectionString = ConfigurationManager.AppSettings["connectionString"]; sqlConnection = new SqlConnection(connectionString); String sqlSelect = "Select OrderID, CustomerID, OrderDate, ShippedDate from Orders"; sqlDataMaster = new SqlDataAdapter(sqlSelect, sqlConnection); sqlConnection.Open(); //=============================================================================== //--- Set up the INSERT Command //=============================================================================== sInsProcName = "prInsert_Order"; insertcommand = new SqlCommand(sInsProcName, sqlConnection); insertcommand.CommandType = CommandType.StoredProcedure; insertcommand.Parameters.Add(new SqlParameter("@nNewID", SqlDbType.Int, 0, ParameterDirection.Output, false, 0, 0, "OrderID", DataRowVersion.Default, null)); insertcommand.UpdatedRowSource = UpdateRowSource.OutputParameters; insertcommand.Parameters.Add(new SqlParameter("@sCustomerID", SqlDbType.NChar, 5,"CustomerID")); insertcommand.Parameters["@sCustomerID"].Value = cmbCust.SelectedValue; insertcommand.Parameters.Add(new SqlParameter("@dtOrderDate", SqlDbType.DateTime, 8,"OrderDate")); insertcommand.Parameters["@dtOrderDate"].Value = dtOrdDt.Text; insertcommand.Parameters.Add(new SqlParameter("@dtShipDate", SqlDbType.DateTime, 8,"ShippedDate")); insertcommand.Parameters["@dtShipDate"].Value = dtShipDt.Text; sqlDataMaster.InsertCommand = insertcommand; //=============================================================================== //--- Set up the UPDATE Command //=============================================================================== sUpdProcName = "prUpdate_Order"; updatecommand = new SqlCommand(sUpdProcName, sqlConnection); updatecommand.CommandType = CommandType.StoredProcedure; updatecommand.Parameters.Add(new SqlParameter("@nOrderID", SqlDbType.Int, 4, "OrderID")); updatecommand.Parameters.Add(new SqlParameter("@dtOrderDate", SqlDbType.DateTime, 8, "OrderDate")); updatecommand.Parameters.Add(new SqlParameter("@dtShipDate", SqlDbType.DateTime, 8, "ShippedDate")); sqlDataMaster.UpdateCommand = updatecommand; //=============================================================================== //--- Set up the DELETE Command //=============================================================================== sDelProcName = "prDelete_Order"; deletecommand = new SqlCommand(sDelProcName, sqlConnection); deletecommand.CommandType = CommandType.StoredProcedure; deletecommand.Parameters.Add(new SqlParameter("@nOrderID", SqlDbType.Int, 4, "OrderID")); sqlDataMaster.DeleteCommand = deletecommand; dt = new DataTable(); sqlDataMaster.FillSchema(dt, SchemaType.Source); ds = new DataSet(); ds.Tables.Add(dt); bs = new BindingSource(); bs.DataSource = ds.Tables[0]; } public void SetComb() { cmbCust.DataSource = dm.GetData("Select * from Customers order by CompanyName"); cmbCust.DisplayMember = "CompanyName"; cmbCust.ValueMember = "CustomerId"; cmbCust.Text = ""; } private void btnSave_Click(object sender, EventArgs e) { sqlDataMaster.Update((DataTable) bs.DataSource); } and Stored Procedures for Insert/Update/Delete set ANSI_NULLS ON set QUOTED_IDENTIFIER ON GO ALTER PROCEDURE [dbo].[prInsert_Order] -- ALTER PROCEDURE prInsert_Order @sCustomerID CHAR(5), @dtOrderDate DATETIME, @dtShipDate DATETIME, @nNewID INT OUTPUT AS SET NOCOUNT ON INSERT INTO Orders (CustomerID, OrderDate, ShippedDate) VALUES (@sCustomerID, @dtOrderDate, @dtShipDate) SELECT @nNewID = SCOPE_IDENTITY() set ANSI_NULLS ON set QUOTED_IDENTIFIER ON GO ALTER PROCEDURE [dbo].[prUpdate_Order] -- ALTER PROCEDURE prUpdate_Order @nOrderID INT, @dtOrderDate DATETIME, @dtShipDate DATETIME AS UPDATE Orders SET OrderDate = @dtOrderDate, ShippedDate = @dtShipDate WHERE OrderID = @nOrderID set ANSI_NULLS ON set QUOTED_IDENTIFIER ON GO ALTER PROCEDURE [dbo].[prDelete_Order] -- ALTER PROCEDURE prDelete_Order @nOrderID INT AS DELETE Orders WHERE OrderID = @nOrderID In the form CustomerID is selected via combobox which has Display property of CustomerName and Value property of CustomerID. But when clicking save button it shows no error, but it also don't save anything in Orders Table of Northwind....dm.GetData is the method of my Data Access Layer class to just get the info and populate CustomerID combobox. Any help with the code is highly appreciated... Thanks Ahmed

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• Following the Thread in OSB

  - by Antony Reynolds

  Threading in OSB The Scenario I recently led an OSB POC where we needed to get high throughput from an OSB pipeline that had the following logic: 1. Receive Request 2. Send Request to External System 3. If Response has a particular value   3.1 Modify Request   3.2 Resend Request to External System 4. Send Response back to Requestor All looks very straightforward and no nasty wrinkles along the way.  The flow was implemented in OSB as follows (see diagram for more details): Proxy Service to Receive Request and Send Response Request Pipeline   Copies Original Request for use in step 3 Route Node   Sends Request to External System exposed as a Business Service Response Pipeline   Checks Response to Check If Request Needs to Be Resubmitted Modify Request Callout to External System (same Business Service as Route Node) The Proxy and the Business Service were each assigned their own Work Manager, effectively giving each of them their own thread pool. The Surprise Imagine our surprise when, on stressing the system we saw it lock up, with large numbers of blocked threads.  The reason for the lock up is due to some subtleties in the OSB thread model which is the topic of this post.   Basic Thread Model OSB goes to great lengths to avoid holding on to threads.  Lets start by looking at how how OSB deals with a simple request/response routing to a business service in a route node. Most Business Services are implemented by OSB in two parts.  The first part uses the request thread to send the request to the target.  In the diagram this is represented by the thread T1.  After sending the request to the target (the Business Service in our diagram) the request thread is released back to whatever pool it came from.  A multiplexor (muxer) is used to wait for the response.  When the response is received the muxer hands off the response to a new thread that is used to execute the response pipeline, this is represented in the diagram by T2. OSB allows you to assign different Work Managers and hence different thread pools to each Proxy Service and Business Service.  In out example we have the “Proxy Service Work Manager” assigned to the Proxy Service and the “Business Service Work Manager” assigned to the Business Service.  Note that the Business Service Work Manager is only used to assign the thread to process the response, it is never used to process the request. This architecture means that while waiting for a response from a business service there are no threads in use, which makes for better scalability in terms of thread usage. First Wrinkle Note that if the Proxy and the Business Service both use the same Work Manager then there is potential for starvation.  For example: Request Pipeline makes a blocking callout, say to perform a database read. Business Service response tries to allocate a thread from thread pool but all threads are blocked in the database read. New requests arrive and contend with responses arriving for the available threads. Similar problems can occur if the response pipeline blocks for some reason, maybe a database update for example. Solution The solution to this is to make sure that the Proxy and Business Service use different Work Managers so that they do not contend with each other for threads. Do Nothing Route Thread Model So what happens if there is no route node?  In this case OSB just echoes the Request message as a Response message, but what happens to the threads?  OSB still uses a separate thread for the response, but in this case the Work Manager used is the Default Work Manager. So this is really a special case of the Basic Thread Model discussed above, except that the response pipeline will always execute on the Default Work Manager.   Proxy Chaining Thread Model So what happens when the route node is actually calling a Proxy Service rather than a Business Service, does the second Proxy Service use its own Thread or does it re-use the thread of the original Request Pipeline? Well as you can see from the diagram when a route node calls another proxy service then the original Work Manager is used for both request pipelines.  Similarly the response pipeline uses the Work Manager associated with the ultimate Business Service invoked via a Route Node.  This actually fits in with the earlier description I gave about Business Services and by extension Route Nodes they “… uses the request thread to send the request to the target”. Call Out Threading Model So what happens when you make a Service Callout to a Business Service from within a pipeline.  The documentation says that “The pipeline processor will block the thread until the response arrives asynchronously” when using a Service Callout.  What this means is that the target Business Service is called using the pipeline thread but the response is also handled by the pipeline thread.  This implies that the pipeline thread blocks waiting for a response.  It is the handling of this response that behaves in an unexpected way. When a Business Service is called via a Service Callout, the calling thread is suspended after sending the request, but unlike the Route Node case the thread is not released, it waits for the response.  The muxer uses the Business Service Work Manager to allocate a thread to process the response, but in this case processing the response means getting the response and notifying the blocked pipeline thread that the response is available.  The original pipeline thread can then continue to process the response. Second Wrinkle This leads to an unfortunate wrinkle.  If the Business Service is using the same Work Manager as the Pipeline then it is possible for starvation or a deadlock to occur.  The scenario is as follows: Pipeline makes a Callout and the thread is suspended but still allocated Multiple Pipeline instances using the same Work Manager are in this state (common for a system under load) Response comes back but all Work Manager threads are allocated to blocked pipelines. Response cannot be processed and so pipeline threads never unblock – deadlock! Solution The solution to this is to make sure that any Business Services used by a Callout in a pipeline use a different Work Manager to the pipeline itself. The Solution to My Problem Looking back at my original workflow we see that the same Business Service is called twice, once in a Routing Node and once in a Response Pipeline Callout.  This was what was causing my problem because the response pipeline was using the Business Service Work Manager, but the Service Callout wanted to use the same Work Manager to handle the responses and so eventually my Response Pipeline hogged all the available threads so no responses could be processed. The solution was to create a second Business Service pointing to the same location as the original Business Service, the only difference was to assign a different Work Manager to this Business Service.  This ensured that when the Service Callout completed there were always threads available to process the response because the response processing from the Service Callout had its own dedicated Work Manager. Summary Request Pipeline Executes on Proxy Work Manager (WM) Thread so limited by setting of that WM.  If no WM specified then uses WLS default WM. Route Node Request sent using Proxy WM Thread Proxy WM Thread is released before getting response Muxer is used to handle response Muxer hands off response to Business Service (BS) WM Response Pipeline Executes on Routed Business Service WM Thread so limited by setting of that WM.  If no WM specified then uses WLS default WM. No Route Node (Echo functionality) Proxy WM thread released New thread from the default WM used for response pipeline Service Callout Request sent using proxy pipeline thread Proxy thread is suspended (not released) until the response comes back Notification of response handled by BS WM thread so limited by setting of that WM.  If no WM specified then uses WLS default WM. Note this is a very short lived use of the thread After notification by callout BS WM thread that thread is released and execution continues on the original pipeline thread. Route/Callout to Proxy Service Request Pipeline of callee executes on requestor thread Response Pipeline of caller executes on response thread of requested proxy Throttling Request message may be queued if limit reached. Requesting thread is released (route node) or suspended (callout) So what this means is that you may get deadlocks caused by thread starvation if you use the same thread pool for the business service in a route node and the business service in a callout from the response pipeline because the callout will need a notification thread from the same thread pool as the response pipeline.  This was the problem we were having. You get a similar problem if you use the same work manager for the proxy request pipeline and a business service callout from that request pipeline. It also means you may want to have different work managers for the proxy and business service in the route node. Basically you need to think carefully about how threading impacts your proxy services. References Thanks to Jay Kasi, Gerald Nunn and Deb Ayers for helping to explain this to me.  Any errors are my own and not theirs.  Also thanks to my colleagues Milind Pandit and Prasad Bopardikar who travelled this road with me. OSB Thread Model Great Blog Post on Thread Usage in OSB

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• nHibernate Self Join Mapping

  - by kmoo01

  Hi Guys, This is probably incredibly simple, but I just cant see the wood for the trees at the moment. For brevity, I would like to model a word object, that has related words to it (synonyms), In doing so I could have the following mappings: <class name="Word" table="bs_word"> <id name="Id" column="WordId" type="Int32" unsaved-value="-1"> <generator class="native"> <param name="sequence"></param> </generator> </id> <property name="Key" column="word" type="String" length="50" /> <many-to-one name="SynonymGroup" class="BS.Core.Domain.Synonym, BS.Core" column="SynonymId" lazy="false"/> <class name="Synonym" table="bs_Synonym"> <id name="Id" column="SynonymId" type="Int32" unsaved-value="-1"> <generator class="native"> <param name="sequence"></param> </generator> </id> <property name="Alias" column="Alias" type="String" length="50" /> <bag name="Words" cascade="none" lazy="false" inverse="true"> <key column="SynonymId" /> <one-to-many class="Word" /> </bag> Mapping it like this would mean for a given word, I can access related words (synonyms) like this: word.SynonymGroup.Words However I would like to know if it is possible to map a bag of objects on an instance of a word object...if that makes sense, so I can access the related words like this: word.Words I've tried playing around with the map element, and composite elements, all to no avail - so I was wondering if some kind person could point me in the right direction? ta, kmoo01

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• I want to find the span tag beween the LI tag and its attributes but no luck.

  - by Mahesh

  I want to find the span tag beween the LI tag and its attributes. Trying with beautful soap but no luck. Details of my code. Is any one point me right methodlogy In this this code, my getId function should return me id = "0_False-2" Any one know right method? from BeautifulSoup import BeautifulSoup as bs import re html = '<ul>\ <li class="line">&nbsp;</li>\ <li class="folder-open-last" id="0">\ <img style="float: left;" class="trigger" src="/media/images/spacer.gif" border="0">\ <span class="text" id="0_False">NOC</span><ul style="display: block;"><li class="line">&nbsp;</li><li class="doc" id="1"><span class="active text" id="0_False-1">PNQAIPMS1</span></li><li class="line">&nbsp;</li><li class="doc-last" id="2"><span class="text" id="0_False-2">PNQAIPMS2</span></li><li class="line-last"></li></ul></li><li class="line-last"></li>\ </ul>' def getId(html, txt): soup = bs(html) soup.findAll('ul',recursive=False) head = soup.contents[0] temp = head elements = {} while True: # It temp is None that means no HTML tags are available if temp == None: break #print temp if re.search('li', str( temp)) != None: attr = str(temp.attrs).encode('ascii','ignore') attr = attr.replace(' ', '') attr = attr.replace('[', '') attr = attr.replace(']', '') attr = attr.replace(')', '') attr = attr.replace('(', '') attr = attr.replace('u\'', '') attr = attr.replace('\'', '') attr = attr.split(',') span = str(temp.text) if span == txt: return attr[3] temp = temp.next else: temp = temp.next id = getId(html,"PNQAIPMS2") print "ID = " + id

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• How to prevent Hibernate from nullifying relationship column during entity removal

  - by Grzegorz

  I have two entities, A and B. I need to easily retrieve entities A, joined with entities B on the condition of equal values of some column (some column from A equal to some column in B). Those columns are not primary or foreign keys, they contain same business data. I just need to have access from each instance of A to the collection of B's with the same value of this column. So I model it like this: class A { @OneToMany @JoinColumn(name="column_in_B", referencedColumnName="column_in_A") Collection<B> bs; This way, I can run queries like "select A join fetch a.bs b where b...." (Actually, the real relationship here is many-to-many. But when I use @ManyToMany, Hibernate forces me to use join table, which doesnt exist here. So I have to use @OneToMany as workaround). So far so good. The main problem is: whenever I delete an instance of A, hibernate calls "Update B set column_in_B = null", becuase it thinks the column_in_B is foreign key pointing at primary key in A (and because row in A is deleted, it tries to clean the foreign key in B). BUT the column_in_B IS NOT a foreign key, and can't be modified, because it causes data lost (and this column is NOT NULL anyway in my case, causing data integerity exception to be thrown). Plese help me with this. How to model such relationships with Hibernate? (I would call it "virtual relationships", or "secondary relationships" or so: as they are not based on foreign keys, they are just some shortcuts which allows for retrieving related objects and quering for them with HQL)

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• Have any software engineers gotten math degrees later in their careers?

  - by vin

  I have a bachelors in computer science and worked the last 12 years as a software engineer. I'm bored with doing general development work, so I want to specialize. I'm thinking about getting a master's degree in math so I can build math models and write algorithms to implement them. I'm unsure what type of work I'd do (financial, gaming, graphics, science, research, etc) but I'm open minded. I would need to refresh my undergrad math skills (which are old and faded), but I loved algebra and calculus. I've been working with couple statisticians so I've been finding myself more interested in statistics. Since I'm a parent supporting a household, I would have to continue working while studying. Have any software engineers taken this route? (Specifically, going from BS in comp sci to MS in math.) If so, what advice do you have for coursework, financing, and getting a job that combines programming with advanced math? How abundant are these kinds of jobs? I'm not sure where one starts. Also, how do you hop from a BS to an MS in a different subject?

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• C# WebBrowser Invoke issue

  - by James Jeffrey

  I am logging into facebook using a web browser. Everything works, but the problem is when I invoke the button click I need to check if the password is correct but, the check seems to happen before the button is invoked which makes no sense at all because the checking code is after the invoke. private void Facebook_Login(String username, String password) { webBrowser1.Url = new Uri("http://m.facebook.com"); while (webBrowser1.ReadyState != WebBrowserReadyState.Complete) Application.DoEvents(); HtmlElementCollection inputs = webBrowser1.Document.GetElementsByTagName("input"); foreach(HtmlElement input in inputs) { if (input.GetAttribute("name") == "email") { input.SetAttribute("value", "[email protected]"); } if (input.GetAttribute("name") == "pass") { input.SetAttribute("value", "kelaroostj"); // dont worry that pass wont work lol. } if (input.GetAttribute("name") == "login") { input.InvokeMember("click"); } } while (webBrowser1.ReadyState != WebBrowserReadyState.Complete) Application.DoEvents(); HtmlElementCollection bs = webBrowser1.Document.GetElementsByTagName("b"); foreach(HtmlElement b in bs) { MessageBox.Show(b.InnerHtml); } Log_Message("Logged into Facebook with: [email protected]"); }

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• When is factory method better than simple factory and vice versa?

  - by Bruce

  Hi all Working my way through the Head First Design Patterns book. I believe I understand the simple factory and the factory method, but I'm having trouble seeing what advantages factory method brings over simple factory. If an object A uses a simple factory to create its B objects, then clients can create it like this: A a = new A(new BFactory()); whereas if an object uses a factory method, a client can create it like this: A a = new ConcreteA(); // ConcreteA contains a method for instantiating the same Bs that the BFactory above creates, with the method hardwired into the subclass of A, ConcreteA. So in the case of the simple factory, clients compose A with a B factory, whereas with the factory method, the client chooses the appropriate subclass for the types of B it wants. There really doesn't seem to be much to choose between them. Either you have to choose which BFactory you want to compose A with, or you have to choose the right subclass of A to give you the Bs. Under what circumstances is one better than the other? Thanks all!

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• How to display panels with component in frame

  - by terence6

  Why my JFrame 'frame' is diplaying empty window, when it should give me 3 menu buttons and my own painted JComponent below ? What am I missing here ? import java.awt.*; import javax.swing.*; public class Eyes extends JFrame { public static void main(String[] args) { final JFrame frame = new JFrame("Eyes"); frame.setPreferredSize(new Dimension(450, 300)); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); JPanel players = new JPanel(new GridLayout(1, 3)); players.add(new JButton("Eyes color")); players.add(new JButton("Eye pupil")); players.add(new JButton("Background color")); JPanel eyes = new JPanel(); eyes.add(new MyComponent()); JPanel content = new JPanel(); content.setLayout(new BoxLayout(content, BoxLayout.Y_AXIS)); content.add(players); content.add(eyes); frame.getContentPane(); frame.pack(); frame.setVisible(true); } } class MyComponent extends JComponent { public MyComponent(){ } @Override public void paint(Graphics g) { int height = 120; int width = 120; Graphics2D g2d = (Graphics2D) g; g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON); BasicStroke bs = new BasicStroke(3.0f); g2d.setStroke(bs); g2d.setColor(Color.yellow); g2d.fillOval(200, 200, height, width); g2d.setColor(Color.black); g2d.drawOval(60, 60, height, width); } }

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• Makefile; mirroring a growing tree through a process

  - by Martineau

  I would like to periodically mirror a growing tree, say, from $in to $out, doing a process in between (saving the only file header). As; #!/bin/bash in=./segd out=./db for f in `find $in -name "*.segd"`;do # Deduct output (dir + name) d=`dirname $f|perl -pe 's!'$in'!'$out'!'` n=`basename $f|perl -pe 's!$!_hdr!'` if [ ! -e $d/$n ]; then [ ! -d $d ] && mkdir -p $d; printf "From %s now build %s\n" $f "$d/$n" # Do something, whathever. For example e.g; dd if=$f bs=32 count=1 conv=swab 2>/dev/null|od -x > $d/$n fi done That is about fair. However; to be more robust, for a better synchronization (say if a source file did change or whatever), I would like to use a Makefile, as in; HDR := $(patsubst ./segd/%.segd,./db/%.segd_hdr,$(wildcard ./segd/*.segd)) all: ${HDR} db/%.segd_hdr: ./segd/%.segd echo "Doing" dd if=$< bs=32 count=1 conv=swab 2>/dev/null|od -x > $@ My problem; I cannot code this Makefile to "dive" more deeply within the source ./segd tree. How can we do it and is there a way ? Many thanks for your kind recommendations. PS: The idea will be to later rsync the (smaller) destination tree over a sat connection.

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• problem when view the super block in ext3 file system

  - by xuczhang

  I tried to view the superblock by command "dd" in ext3 file system. dd if=/dev/sda3 bs=4096 skip=1 count=1 of=superblock But the result in superblock file is not correct(I compare the value of Inodes count I got from dumpe2fs). The device file /dev/sda3 is started at the boot block and then the superblock of the group0? And another question is the boot block and superblock's size are both BLOCKSIZE(here is 4096)? The disk format of ext2/ext3(I think they are the same) are shown below:

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• Linux buffer cache effect on IO writes?

  - by Patrick LeBoutillier

  I'm copying large files (3 x 30G) between 2 filesystems on a Linux server (kernel 2.6.37, 16 cores, 32G RAM) and I'm getting poor performance. I suspect that the usage of the buffer cache is killing the I/O performance. To try and narrow down the problem I used fio directly on the SAS disk to monitor the performance. Here is the output of 2 fio runs (the first with direct=1, the second one direct=0): Config: [test] rw=write blocksize=32k size=20G filename=/dev/sda # direct=1 Run 1: test: (g=0): rw=write, bs=32K-32K/32K-32K, ioengine=sync, iodepth=1 Starting 1 process Jobs: 1 (f=1): [W] [100.0% done] [0K/205M /s] [0/6K iops] [eta 00m:00s] test: (groupid=0, jobs=1): err= 0: pid=4667 write: io=20,480MB, bw=199MB/s, iops=6,381, runt=102698msec clat (usec): min=104, max=13,388, avg=152.06, stdev=72.43 bw (KB/s) : min=192448, max=213824, per=100.01%, avg=204232.82, stdev=4084.67 cpu : usr=3.37%, sys=16.55%, ctx=655410, majf=0, minf=29 IO depths : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%, >=64=0.0% submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0% complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0% issued r/w: total=0/655360, short=0/0 lat (usec): 250=99.50%, 500=0.45%, 750=0.01%, 1000=0.01% lat (msec): 2=0.01%, 4=0.02%, 10=0.01%, 20=0.01% Run status group 0 (all jobs): WRITE: io=20,480MB, aggrb=199MB/s, minb=204MB/s, maxb=204MB/s, mint=102698msec, maxt=102698msec Disk stats (read/write): sda: ios=0/655238, merge=0/0, ticks=0/79552, in_queue=78640, util=76.55% Run 2: test: (g=0): rw=write, bs=32K-32K/32K-32K, ioengine=sync, iodepth=1 Starting 1 process Jobs: 1 (f=1): [W] [100.0% done] [0K/0K /s] [0/0 iops] [eta 00m:00s] test: (groupid=0, jobs=1): err= 0: pid=4733 write: io=20,480MB, bw=91,265KB/s, iops=2,852, runt=229786msec clat (usec): min=16, max=127K, avg=349.53, stdev=4694.98 bw (KB/s) : min=56013, max=1390016, per=101.47%, avg=92607.31, stdev=167453.17 cpu : usr=0.41%, sys=6.93%, ctx=21128, majf=0, minf=33 IO depths : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%, >=64=0.0% submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0% complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0% issued r/w: total=0/655360, short=0/0 lat (usec): 20=5.53%, 50=93.89%, 100=0.02%, 250=0.01%, 500=0.01% lat (msec): 2=0.01%, 4=0.01%, 10=0.01%, 20=0.01%, 50=0.12% lat (msec): 100=0.38%, 250=0.04% Run status group 0 (all jobs): WRITE: io=20,480MB, aggrb=91,265KB/s, minb=93,455KB/s, maxb=93,455KB/s, mint=229786msec, maxt=229786msec Disk stats (read/write): sda: ios=8/79811, merge=7/7721388, ticks=9/32418456, in_queue=32471983, util=98.98% I'm not knowledgeable enough with fio to interpret the results, but I don't expect the overall performance using the buffer cache to be 50% less than with O_DIRECT. Can someone help me interpret the fio output? Are there any kernel tunings that could fix/minimize the problem? Thanks a lot,

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• Linux buffer cache effect on IO writes?

  - by Patrick LeBoutillier

  Hi, I'm copying large files (3 x 30G) between 2 filesystems on a Linux server (kernel 2.6.37, 16 cores, 32G RAM) and I'm getting poor performance. I suspect that the usage of the buffer cache is killing the I/O performance. To try and narrow down the problem I used fio directly on the SAS disk to monitor the performance. Here is the output of 2 fio runs (the first with direct=1, the second one direct=0): Config: [test] rw=write blocksize=32k size=20G filename=/dev/sda # direct=1 Run 1: test: (g=0): rw=write, bs=32K-32K/32K-32K, ioengine=sync, iodepth=1 Starting 1 process Jobs: 1 (f=1): [W] [100.0% done] [0K/205M /s] [0/6K iops] [eta 00m:00s] test: (groupid=0, jobs=1): err= 0: pid=4667 write: io=20,480MB, bw=199MB/s, iops=6,381, runt=102698msec clat (usec): min=104, max=13,388, avg=152.06, stdev=72.43 bw (KB/s) : min=192448, max=213824, per=100.01%, avg=204232.82, stdev=4084.67 cpu : usr=3.37%, sys=16.55%, ctx=655410, majf=0, minf=29 IO depths : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%, >=64=0.0% submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0% complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0% issued r/w: total=0/655360, short=0/0 lat (usec): 250=99.50%, 500=0.45%, 750=0.01%, 1000=0.01% lat (msec): 2=0.01%, 4=0.02%, 10=0.01%, 20=0.01% Run status group 0 (all jobs): WRITE: io=20,480MB, aggrb=199MB/s, minb=204MB/s, maxb=204MB/s, mint=102698msec, maxt=102698msec Disk stats (read/write): sda: ios=0/655238, merge=0/0, ticks=0/79552, in_queue=78640, util=76.55% Run 2: test: (g=0): rw=write, bs=32K-32K/32K-32K, ioengine=sync, iodepth=1 Starting 1 process Jobs: 1 (f=1): [W] [100.0% done] [0K/0K /s] [0/0 iops] [eta 00m:00s] test: (groupid=0, jobs=1): err= 0: pid=4733 write: io=20,480MB, bw=91,265KB/s, iops=2,852, runt=229786msec clat (usec): min=16, max=127K, avg=349.53, stdev=4694.98 bw (KB/s) : min=56013, max=1390016, per=101.47%, avg=92607.31, stdev=167453.17 cpu : usr=0.41%, sys=6.93%, ctx=21128, majf=0, minf=33 IO depths : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%, >=64=0.0% submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0% complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0% issued r/w: total=0/655360, short=0/0 lat (usec): 20=5.53%, 50=93.89%, 100=0.02%, 250=0.01%, 500=0.01% lat (msec): 2=0.01%, 4=0.01%, 10=0.01%, 20=0.01%, 50=0.12% lat (msec): 100=0.38%, 250=0.04% Run status group 0 (all jobs): WRITE: io=20,480MB, aggrb=91,265KB/s, minb=93,455KB/s, maxb=93,455KB/s, mint=229786msec, maxt=229786msec Disk stats (read/write): sda: ios=8/79811, merge=7/7721388, ticks=9/32418456, in_queue=32471983, util=98.98% I'm not knowledgeable enough with fio to interpret the results, but I don't expect the overall performance using the buffer cache to be 50% less than with O_DIRECT. Can someone help me interpret the fio output? Are there any kernel tunings that could fix/minimize the problem? Thanks a lot,

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