Date: Sun, 25 Apr 1999 00:58:34 -0400 (EDT) From: Mikhail Teterin <mi@kot.ne.mediaone.net> To: ken@plutotech.com (Kenneth D. Merry) Cc: dnelson@emsphone.com, freebsd-scsi@FreeBSD.ORG Subject: Re: writing slower with SoftUpdates Message-ID: <199904250458.AAA03413@kot.ne.mediaone.net> In-Reply-To: <199904250146.TAA48692@panzer.plutotech.com> from "Kenneth D. Merry" at "Apr 24, 1999 07:46:17 pm"
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Kenneth D. Merry once stated: => > > WCE was ON on both drives: => > > => > > Checking SCSI drives for write-cache: => > > <SEAGATE ST39102LW 0006> at scbus0 target 8 lun 0 (pass0,da0) => > > <SEAGATE ST39102LW 0006> at scbus0 target 9 lun 0 (pass1,da1) => > > I disabled WCE on both and re-ran the iozone tests. No noticable => > > changes from the previous numbers... What really bothers me, is the => > > fact that reading speed speed is consistently only 13-14Mb/s on one => > > disk, while it is 17-18 (same as writing) on the other. =Try the physical sector format: = camcontrol defects -u 0 -f phys -G Got 0 defects. camcontrol defects -u 1 -f phys -G Got 0 defects. =To get both: camcontrol defects -u 0 -f phys -PG | wc -l Got 868 defects: 868 camcontrol defects -u 1 -f phys -PG | wc -l Got 141 defects: 141 Khmm, the second disk is indeed faster for writing and a LOT faster for reading. Does this number of defects justify an exhange request -- we just bought both disks? Why do SoftUpdates slow things down on both disks, anyway? With and without WCE -- the numbers don't change noticeably... => The machine is 350MHz PentumII with 128Mb of 100MHz RAM. The disks => are LVD being the only targets on the LVD outlet of Adaptec 2940U2W. =One other thing to look at is where you are on the disk. I/O =performance will be better on the outer diameter tracks. I know, but the partitions are identical: mi@labservn:~ (95) mount | grep /tmp /dev/da0s1e on /tmp (local, soft-updates, writes: sync 4 async 8014) /dev/da1s1e on /var/tmp (local, soft-updates, writes: sync 23 async 4801) mi@labservn:~ (96) ( disklabel da0 ; disklabel da1 ) | grep ' e:' e: 1048576 655360 4.2BSD 0 0 0 # (Cyl. 963*- 2505*) e: 1048576 655360 4.2BSD 0 0 0 # (Cyl. 963*- 2505*) Thanks a lot for your help! -mi To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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