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Re: Tests of RAID adapters

From: Francois Tigeot <ftigeot@xxxxxxxxxxxx>
Date: Wed, 27 Apr 2011 20:43:01 +0200

On Wed, Apr 27, 2011 at 02:18:49PM +0200, Francois Tigeot wrote:
> On Mon, Apr 25, 2011 at 07:38:57PM +0200, Sascha Wildner wrote:
> > On 4/25/2011 9:12, Francois Tigeot wrote:
> > >LSI SAS 3081E-R
> > >---------------
> > I've put an update for mpt(4) here:
> > http://leaf.dragonflybsd.org/~swildner/0001-mpt-4-Sync-with-FreeBSD.patch
> 2. newfs_hammer completes succesfully, although performance is bad

The bad performance was caused by disabled write-cache on the disks.

MPT SAS controllers disable disk cache for writes by default and do not
allow the user to enable it in their BIOS setup.

The disks I used can read/write linearly at about 135 MB/s.

On startup, linear read speed on the array is 133 MB/s, and write speed
is an abysmal 13.50 MB/s (no, it's not a typo)

Fortunately, it's possible to enable write-cache again with a sysctl:

# sysctl -w hw.mpt0.vol_member_wce="On"

After typing that command, linear speeds became 136 MB/s for reads and
132 MB/s for writes.

Francois Tigeot

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