NFS Performance (was Re: [Beowulf] GPFS on Linux (x86))

Chris Samuel csamuel at
Wed Nov 8 18:57:26 PST 2006

On Saturday 16 September 2006 00:32, Brent Franks wrote:

> On 9/15/06, Chris Samuel <csamuel at> wrote:
> > Wild guess - NFS servers are running RHEL and using ext3 ?
> Exactly.

If you are using RHEL4 and are not at Update 4 already then apparently there 
is a RH induced bug in the default cfq io_scheduler and the work around is 
(according to Oracle at least [1]) to set the node to use the deadline 
scheduler at boot time as well.

The better fix is apparently to update to RHEL4 U4.

[1] - Their OCFS2 page says:

# RHEL4 U2 and U3 users are advised to use the DEADLINE io scheduler instead
# of the default CFQ due to Bugzilla# 184535.  (Ed: [2])

[2] -

 Christopher Samuel - (03)9925 4751 - VPAC Deputy Systems Manager
 Victorian Partnership for Advanced Computing
 Bldg 91, 110 Victoria Street, Carlton South, VIC 3053, Australia

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