strange performance dip shown by iozone

mi+mx_at_aldan.algebra.com
Date: 02/18/04

  • Next message: David Schultz: "Re: strange performance dip shown by iozone" 
    To: fs@FreeBSD.org, performance@FreeBSD.org
Date: Wed, 18 Feb 2004 17:29:06 -0500

    Hello!

    I'm trying to tune the amrd-based RAID5 and have made several iozone
    runs on the array and -- for comparision -- on the single disk connected
    to the Serial ATA controller directly.

    The RAID-based FS was newfs-ed with ``-b 65536'', as it is intended to
    store very large files. The single-disk FS was newfs-ed with defaults.

    No softupdates were enabled on either, since those seem to degrade iozone
    results slightly (iozone reads/writes a single file anyway).

    The filesystems displayed different performance (reads are better with
    RAID, writes -- with the single disk), but both have shown a notable dip
    in writing (and re-writing) speed when iozone used the record lengthes
    of 128 and 256. Can someone explain that? Is that a known fact? How can
    that be avoided?

    The machine is an amd64 running a fresh -current. The disks are 200Gb
    SATAs. RAID5 consists of 6 of them.

    Thanks!

            -mi

    _______________________________________________
    freebsd-performance@freebsd.org mailing list
    http://lists.freebsd.org/mailman/listinfo/freebsd-performance
    To unsubscribe, send any mail to "freebsd-performance-unsubscribe@freebsd.org"

  • Next message: David Schultz: "Re: strange performance dip shown by iozone"