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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