From owner-freebsd-stable@FreeBSD.ORG  Tue Mar 27 17:54:46 2007
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Date: Tue, 27 Mar 2007 18:52:40 +0100
From: Richard Tector <richardtector@thekeelecentre.com>
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Subject: Dell SAS5 Performance Issue
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I'm suffering from very slow write performance on a Dell PowerEdge 860 
with the SAS5/IR controller (mpt driver) running either 6.2-RELEASE or 
6.2-STABLE with sources from yesterday. The controller hosts 2 Western 
Digital 320GB SATA disks in a RAID1 configuration.
Reads approach 65MB/s however writes appear extremely slow, in the 
region of 6-7MB/s with a dd and a blocksize of 1MB all the way down to 
about 300KB/s while extracting a ports snapshot.

It was suggested to me that perhaps write caching has been disabled on 
the controller however no options exist within the BIOS configuration to 
view/adjust *any* caching options.

Has anyone else experienced this issue? If so how did they resolve it?
Also, is there any way to toggle the caching settings from FreeBSD?

Regards,

Richard Tector