Re: Software RAID5 with 2.6.0-test

From: Måns Rullgård (mru_at_users.sourceforge.net)
Date: 10/09/03

  • Next message: Xose Vazquez Perez: "2.4.22-bk30 and C trigraphs bugs" 
    To: linux-kernel@vger.kernel.org
Date:	Thu, 09 Oct 2003 01:44:13 +0200

    Torrey Hoffman <thoffman@arnor.net> writes:

    > My experience:
    >
    > I'm running 2.6.0-test6 on a dual pentium 3 with software raid-5 across
    > 5 disks on two different IDE hardware controllers (VIA and Promise).
    > I've got a 224 GB reiserfs partition on that.
    >
    > After 8 days uptime, it doesn't seem to have blown up yet. However I
    > don't stress it heavily - just a nightly rsync or two which does a lot
    > of reading and writing, and I export my music collection on it via NFS,
    > which is a low level of read activity.

    When I tried it, I was running 2.6.0-test4. The RAID5 was 4 120 GB
    Seagate disks on a Highpoint controller. On top of that, I had LVM,
    with ext3 fs. After just minutes, strange things started happening to
    files. Some had random bits changed in the inode, others were just
    trashed. e2fsck complained a great deal.

    I went back to 2.4.21, which is working OK. A couple of things bother
    me, though. In the dmesg output there are many of these:

    raid5: switching cache buffer size, 8192 --> 1024
    raid5: switching cache buffer size, 1024 --> 4096
    raid5: switching cache buffer size, 4096 --> 1024
    raid5: switching cache buffer size, 1024 --> 4096
    raid5: switching cache buffer size, 4096 --> 1024

    ISTR reading somewhere, that this has a bad impact on performance.

    The other thing that I don't like, is the performance of the RAID
    array. The disks individually give ~40 MB/s read speed, but the array
    only measures 25 MB/s. I was of the impression, that RAID5 would give
    read speeds at least equal to the underlying disks. Is this
    incorrect? 

    -- 
Måns Rullgård
mru@users.sf.net
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  • Next message: Xose Vazquez Perez: "2.4.22-bk30 and C trigraphs bugs"

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