|Subject:||Bonnie getc reading hitting exact 65536 kb/s|
|From:||"A. Liemen" <maillist@xxxxxxxxxx>|
|Date:||Sat, 15 Jul 2006 19:13:10 +0200|
|User-agent:||Thunderbird 18.104.22.168 (Windows/20060516)|
during some xfs tuning tests I discovered the following phenomenon. Maybe someone can explain it to me:
Bonnie++ Reading with getc()... hits exactly an almost constant 65536 kbyte/s with only ~15% IO usage.
iostat and bonnie output can be found under:
sdb is a 14 disk RAID10 (128kb stripe) 2.8Tbyte XFS Volume with an external log (128Mb) on sda7 (Raid1)
mount options are:
mkfs.xfs -f -d sunit=256,swidth=1792 -l version=2,size=128m,logdev=/dev/sda7 /dev/sdb
system: - debian testing 2.6.15-1-amd64-k8-smp - dual opteron 275-285 (both tested) - 16gb ram - areca pci-x 1160 controller 1gb cache v1.41 firmware - WD400YR disks
CPU usage is 100% (on one of the cpus) but i don't think that's the limiting factor since it hits that 16bit value absolut constantly.
I have also tested it with exactly the same server but faster CPUs and it's hitting the same barrier + tested it with no mkfs.xfs options + no mount options on a second identical server. Same problem.
Intelligent reading is way above with 350+ Mb/s (check bonnie.txt)
Also of interest would be why the random seeks are so bad.
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