'poor perc 6/i performance'

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List:       linux-poweredge
Subject:    poor perc 6/i performance
From:       "Ryan Dooley" <ryan.dooley () gmail ! com>
Date:       2008-03-28 16:02:10
Message-ID: be540f470803280902j10ce86a4sd7ed2892abff32f9 () mail ! gmail ! com
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I've a 2950, 3rd generation system, with 6 15K SAS drives attached to the
PERC 6/i.  It's running CentOS 5.1 (kernel 2.6.18-53).  Each of the disks
are in jbod mode (6 virtual raid0 devices).
In comparison to another host from another vendor, I have two machines that
are virtually identical (same ram, same cpus).  The only things that are
different are the motherboards and an aic94xx controller for the disks in
the comparison system (which is from Supermicro).

The aic94xx controller seems to do better under heavy load (think multiple
workers accessing the same data on the disk, rather database like).

We use md to create a raid0 software raid across a partition on each of the
disks.  The disks on both systems are Seagate 15K 146G sas disks (the only
difference seems to be the revision number, both systems have the same
model).

The dell seems to get about 66-67% of the read performance in comparison to
the SuperMicro machine.

I don't see a whole lot of tweakables for the megaraid_sas driver so I'm
curious if anybody else has seen this behavior?

Cheers,
Ryan

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I&#39;ve a 2950, 3rd generation system, with 6 15K SAS drives attached to the PERC \
6/i. &nbsp;It&#39;s running CentOS 5.1 (kernel 2.6.18-53). &nbsp;Each of the disks \
are in jbod mode (6 virtual raid0 devices).<div><br></div><div>In comparison to \
another host from another vendor, I have two machines that are \
virtually&nbsp;identical&nbsp;(same ram, same cpus). &nbsp;The only things that are \
different are the motherboards and an aic94xx controller for the disks in the \
comparison system (which is from Supermicro).</div> <div><br></div><div>The aic94xx \
controller seems to do better under heavy load (think multiple workers accessing the \
same data on the disk, rather database like).&nbsp;</div><div><br></div><div>We use \
md to create a raid0 software raid across a&nbsp;partition&nbsp;on each of the disks. \
&nbsp;The disks on both systems are Seagate 15K 146G sas disks (the only difference \
seems to be the revision number, both systems have the same model).</div> \
<div><br></div><div>The dell seems to get about 66-67% of the read performance \
in&nbsp;comparison&nbsp;to the SuperMicro machine.</div><div><br></div><div>I \
don&#39;t see a whole lot of tweakables for the megaraid_sas driver so I&#39;m \
curious if anybody else has seen this behavior?</div> \
<div><br></div><div>Cheers,</div><div>Ryan</div>

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