From owner-freebsd-scsi  Sat Apr 24 21:59:52 1999
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From: Mikhail Teterin <mi@kot.ne.mediaone.net>
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Subject: Re: writing slower with SoftUpdates
In-Reply-To: <199904250146.TAA48692@panzer.plutotech.com> from "Kenneth D. Merry" at "Apr 24, 1999 07:46:17 pm"
To: ken@plutotech.com (Kenneth D. Merry)
Date: Sun, 25 Apr 1999 00:58:34 -0400 (EDT)
Cc: dnelson@emsphone.com, freebsd-scsi@FreeBSD.ORG
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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


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