[Beowulf] Raid disk read performance issue in Linux 2.6, anyone seen this?
ctierney at HPTI.com
Sat Dec 4 09:42:41 PST 2004
I have noticed some significant differences in disk performance
when moving some of my cluster I/O servers from linux-2.4 to
linux-2.6. For several different raid systems with several
linux-2.6 kernel and distributions, the read performance is
Distros: SuSE 9.1 Professional AMD64, Redhat 4.0 beta, IA64
Kernels: Standard distro kernels, also tried stock 2.6.9 on
For the 2.4 kernels, I needed to tweak /proc/sys/vm/max_readahead
to improve performance. In 2.6, the command is blockdev --setra.
Using blockdev helps some, but not much. Adjusting blockdev
gets performance for one raid system from 10 MB/s to 30 MB/s. Under
2.4 the read performance is 90 MB/s.
I looked at a few of the anticipatory scheduler options and also
tried using the deadline scheduler. Nothing helped.
This problem appears on different storage. I have tried DDN (raid 3),
Nexsan (raid 5), and Infotrend (raid 3 and 5).
For those using PVFS1/2, Lustre, or building fast NFS servers
with Linux 2.6, have you seen this?
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