Date: Tue, 6 Jan 2004 15:03:46 -0500 From: "Derek Marcotte" <derek@cpainc.ca> To: "Dan Nelson" <dnelson@allantgroup.com> Cc: questions@freebsd.org Subject: Re: Poor SCSI disk preformance [more on camcontrol please!] Message-ID: <088a01c3d490$31993850$0301a8c0@office.cpainc.net> References: <000201c3d461$eea71770$0301a8c0@office.cpainc.net> <012d01c3d47d$40fe8b50$f4f0a8c0@pcmedx.com> <086401c3d481$d35e2ce0$0301a8c0@office.cpainc.net> <20040106194244.GJ38169@dan.emsphone.com>
next in thread | previous in thread | raw e-mail | index | archive | help
> Aha. Check the WCE bit to see if your write cache is enabled
on the
> disk
Bingo:
# dd if=/dev/zero of=/dev/da0 bs=64k &
[1] 2253
# iostat -K -w 1 da0
tty da0 cpu
tin tout KB/t tps MB/s us ni sy in id
2 38 0.00 0 0.00 1 0 1 0 98
0 43 64.00 223 13.91 0 0 8 1 91
0 43 64.00 223 13.92 0 0 5 0 95
0 43 64.00 223 13.92 0 0 8 1 91
0 43 64.00 223 13.92 0 0 6 0 94
0 42 64.00 223 13.92 0 0 5 1 94
0 43 64.00 223 13.92 1 0 6 1 92
> Set it by running "cmcontrol mode da0 -m 8 -e -P 2", and set
"WCE: 1"
I needed to modify your command slightly to:
camcontrol mode da0 -m 8 -e -P 0
I guess I don't have a page 2 for some reason... This will
probably cause this bit to be reset on reboot as well, because it
is the current page?
Is it prudent to attempt to set the WCE:1 on all drives that get
attached? I will be formatting a large number of greatly varying
drives, including ATA converted to SCSI type drives, and really
old, and really new drive types.
I've had a look at man camcontrol earlier, but I don't know
enough about the inner workings of SCSI for this to mean much to
me. It seems to be pretty obscure (like how would I know to
enable features/specs to edit a modepage?), but extremely
powerful. Where can I read more about this, is there a good
camcontrol FAQ/tutorial out there that explains what these
details actually mean/do?
Thanks for the help!
Derek
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?088a01c3d490$31993850$0301a8c0>