Disk I/O Performance with CCD

[Bill Vermillion]

Ashes to ashes, and DOS to DOS Kristofer Pettijohn was heard to say 
on or about Tue, Oct 19, 2004 at 14:22 :


> 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?

Why not run one of the benchmarks to see what your disk I/O looks
like through the filesystem.

I've been using the old Iozone 2.1 for about 10 years - it's simple
and only tests throught through the filesystem.  I save a copy
of the output when I first install a system and then if things
appear slow later I'll run it again to see if it did slow down
or that I remembered the speeds differently.

It's under /usr/ports/benchmarks/iozone21.

Bill
-- 
Bill Vermillion - bv @ wjv . com