Date: Tue, 6 Jan 2004 13:42:45 -0600 From: Dan Nelson <dnelson@allantgroup.com> To: Derek Marcotte <derek@cpainc.ca> Cc: Mike Maltese <mike@pcmedx.com> Subject: Re: Poor SCSI disk preformance Message-ID: <20040106194244.GJ38169@dan.emsphone.com> In-Reply-To: <086401c3d481$d35e2ce0$0301a8c0@office.cpainc.net> References: <000201c3d461$eea71770$0301a8c0@office.cpainc.net> <012d01c3d47d$40fe8b50$f4f0a8c0@pcmedx.com> <086401c3d481$d35e2ce0$0301a8c0@office.cpainc.net>
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In the last episode (Jan 06), Derek Marcotte said: > Actually, just for kicks: > > # dd if=/dev/da0 of=/dev/null bs=128k & > [1] 1839 > # iostat -K -w 1 da0 > tty da0 cpu > tin tout KB/t tps MB/s us ni sy in id > 1 42 64.00 607 37.92 1 0 1 0 98 > 0 43 64.00 222 13.87 0 0 2 0 98 > 0 43 64.00 223 13.92 0 0 0 2 98 > 0 42 64.00 224 13.98 0 0 2 0 98 > 0 43 64.00 222 13.86 0 0 3 0 97 > 0 43 64.00 223 13.92 0 0 1 2 98 > 0 43 64.00 223 13.92 0 0 2 1 97 > 0 42 64.00 223 13.92 0 0 3 0 97 > 0 43 64.00 223 13.92 0 0 1 0 99 > > Seems to give me the performance that I expect... Aha. Check the WCE bit to see if your write cache is enabled on the disk: # camcontrol mode da0 -m 8 | grep WCE If it's not set, that could be contributing to the speed difference between reads and writes. Set it by running "cmcontrol mode da0 -m 8 -e -P 2", and set "WCE: 1". -- Dan Nelson dnelson@allantgroup.com
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