From owner-freebsd-scsi  Fri Nov  3 20: 3: 0 2000
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Date: Fri, 03 Nov 2000 22:02:01 -0600
From: Gabor Kincses <gabor@acm.org>
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Hello,

This is all I had to do:

KERNEL config file:
pseudo-device   ccd 4   # Concatenated disk driver

gabor@steinbeck: <1160> cat /etc/ccd.conf
ccd0            512     0 /dev/ad0s3f /dev/ad2s1f

I have been using this since June.   Early on I measured performance and
I got ~75% increased random read and sequential block read/write per
bonnie.  bonnie suffers from file system caching but I ran it with 2x
the size of my ram, which should eliminate caching artifacts.

BTW, the two disks are quite dissimilar (13 and 4 GB), I just made sure
to create identical sized `f' partitions.  Since performance speaks for
itself, I consider the disk geometry a non-issue.  Granted I had to
increase the interleave factor to much bigger than what the man page
recommended to get optimum performance.

You may also want to strip swap like this (/etc/fstab):

/dev/ad0s2b     none        swap    sw      0   0
/dev/ad2s1b     none        swap    sw      0   0

I may have had to fiddle with disklabel when installing, but it wasn't a
big deal, I think I just followed ccdconfig(8).

BTW, does anybody have numbers on IDE disk speeds to help decide if a
third disk would max-out a 33MHz UDMA IDE controller?

-- 
Gabor Kincses
(gabor@acm.org)
Running FreeBSD 4.0-STABLE


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