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Date:      Sat, 24 Jan 2004 22:25:04 -0600
From:      Dan Nelson <dnelson@allantgroup.com>
To:        Rishi Chopra <rchopra@cal.berkeley.edu>
Cc:        questions@freebsd.org
Subject:   Re: Adaptec 2400A Performance
Message-ID:  <20040125042504.GC74242@dan.emsphone.com>
In-Reply-To: <401207EF.7030005@cal.berkeley.edu>
References:  <401207EF.7030005@cal.berkeley.edu>

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In the last episode (Jan 23), Rishi Chopra said:
> I've run some imperical tests on the Adaptec 2400A raid controller
> (results and setup can be seen here):
> 
> http://www.ocf.berkeley.edu/~rchopra/RaidResults.html
> 
> I was rather disappointed with the results.  Can anyone suggest what
> might be causing such slow disk speeds, or whether these speeds are
> out of the ordinary for a 4-disk FreeBSD RAID5 installation?  I have
> done nothing to configure the card aside from striping the array in
> BIOS; FreeBSD seems to automatically detect the disks.
> 
> I once ran a 2-disk RAID-0 installation on Win2k which was 6-7 times
> faster on sequential read/write tests (60-70MB/sec), hence my dismay.

RAID-5 has to do 4 I/Os for every write, which would explain the bad
write performance, but I can't explain your read performance.  It's not
strictly comparable, but a Raid-5 4x73gb SCSI setup using an Adaptec
3200S (128MB cache), which looks like it uses the same RAID engine and
firmware as your 2400A, averages 18MB/sec writes and 50MB/sec reads. 
Your card configured with a RAID 0 volume should equal your w2k speeds.
 
-- 
	Dan Nelson
	dnelson@allantgroup.com



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