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Re: XFS + SMP + Software RAID 5 slow?

To: Simon Matter <simon.matter@xxxxxxxxxxxxxxxx>
Subject: Re: XFS + SMP + Software RAID 5 slow?
From: Andrew Klaassen <ak@xxxxxxx>
Date: Fri, 31 Oct 2003 18:31:30 -0500
Cc: linux-xfs@xxxxxxxxxxx
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On Sat, Nov 01, 2003 at 12:14:45AM +0100,
Simon Matter wrote:

> > On Fri, Oct 31, 2003 at 04:50:13PM -0500,
> > Andrew Klaassen wrote:
> >
> >> I've been experiencing *very* slow sustained write ( <
> >> .5MB/sec) using 2.4.20-20.9.XFS1.3.1smp on a dual-Xeon box
> >> with a 3ware 7506 card in JBOD mode.  Software RAID 5.  No
> >> such problems with Ext3 ( > 20MB/sec sustained write) with
> >> the same kernel on the same software RAID 5 device. 
> >> Obviously there's something very wrong here.
> >>
> >> Known issue?  Any idea what might be causing this?
> >
> > By the way: Using hardware RAID 5 on exactly the same setup,
> > the XFS and EXT3 numbers are virtually identical (~5MB/sec
> > sustained write).  Only software RAID 5 seems to cause this
> > great divergence.
> 
> Did you try your setup with an external log? IIRC the problem
> with bad write performance on software RAID 5 should have been
> adressed and mostly fixed with the XFS1.3.x release. I
> recommend to try with external log anyway. I never had good
> results on my software RAID 5 configurations until I used
> external log. However, I never did my tests again in the
> XFS1.3.x days.

No, I haven't.  I'll give that a try.

Andrew Klaassen


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