Disk I/O Performance with CCD

Kristofer Pettijohn krishopper at cybernetik.net
Tue Oct 19 12:34:23 PDT 2004

Im looking for some suggestions on I/O performance.

I'm using FreeBSD 4.10-RELEASE on a Usenet transit server running
Diablo for the transit software.

I have 4 Seagate ST373435LC SCSI drives, 70GB each, and I am using
CCD to bind them together with RAID-0 stripes.

I can pull in anywhere from 30-40 MB sec and push out ~ 8-15 MB/sec..
averaging about 50 MB/sec throughput.. feeds coming in are coming
in just fine, but sending stuff back out is lagging behind.. its
falling about a half hour behind every hour.

I've used tunefs to set the average file size to 20 MB and enabled
soft-updates, as these are generally larger binary files that just
get appended to, and then seeked later on to send the article out,
I've played with setting the stripe size from anywhere between 8MB
and 64MB, and did not see much change on performance between those.

Maybe I'm just missing something small, but on these SCSI drives
which have 160 MB/s transfer rates, I'm expecting a bit more than
I'm getting with CCD.

Can someone give me any pointers to look at or suggestions of things
to try?



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