Re: Disk I/O Performance with CCD

From: Bill Vermillion (bv_at_wjv.com)
Date: 10/19/04

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    Date: Tue, 19 Oct 2004 17:18:26 -0400
To: Kristofer Pettijohn <krishopper@cybernetik.net>

    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
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