Correction: The fio test completes in 4 minutes on Alpha. On 07/27/2011 06:22 PM, William King wrote:
Problem: I have run into what appears to be a driver problem with the Seagate Barracuda 7200.12 drives. The symptom is io load of 10-15 times the load for other drives. To the point the box becomes fully io-bound and unresponsive when even installing apt packages or rsync of a 100MB file. Background: I have two servers with nearly identical hardware: Alpha has Seagate Barracuda 7200.12 1TB drives model: ST31000528AS and Bravo that has Western Digital Cavaliar Black 1TB model: 'WDC WD1001FALS-0'. Both servers have Ubuntu 11.04 64bit server installed, and have fully updated to the 2.3.38-10 kernel. More hardware info and logs can be located here: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/815540 The server hardware manufacturer page is: http://www.supermicro.com/Aplus/system/1U/1042/AS-1042G-TF.cfm Command outputs: # lspci |grep SATA 00:11.0 SATA controller: ATI Technologies Inc SB7x0/SB8x0/SB9x0 SATA Controller [AHCI mode] # uname -a Linux alpha-mule 2.6.38-10-server #46-Ubuntu SMP Tue Jun 28 16:31:00 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux Steps to confirm/reproduce and narrow scope: I have taken the hard drives from Bravo, put them into Alpha reinstalled and there is no problem. Also I have placed some older Seagate Barracuda 7200.9 80GB drives in Alpha and the problem does not exist then either. I used iotop and iostats to watch the reported io load as well as the read/write speeds to the disk. I then used rsync with a bandwidth limitation to measure the performance difference between the two servers in terms of server load and iotop reported IO%. A cat of /proc/interrupts show an order of magnitude more interrupts for ahci on Alpha than Bravo for the same amount of traffic during an rsync. I have hdparm -t /dev/sda test and have seen a performance of ~50MB/s on the Seagate 7200.12 drive while the specs and other benchmarks claim speeds of up to 140MB/s. The Western Digital in the same hardware are able to reach speeds of ~105MB/s and the Seagate 7200.9 gets ~65MB/s. The hard drive was not in use at the time of the hdparm test. I took a perf capture of a fio random read test on each machines. The test completes in 4 seconds on Alpha and 2 minutes 45 seconds on Bravo and the perf stats show all the extra time being spent in the kernel scheduler section. I initially had the Seagate hard drives on firmware CC46 then updated them to the latest firmware of CC49. No change detected between firmwares. I have setup alpha to be able to rebuild the Ubuntu Kernel with patches so I can easily test new changes. Also I have the linux kernel git tree cloned so while it would be possible, I would be more comfortable testing on the Ubuntu version of the 2.6.38-10 kernel. -William King
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