Re: kernel: swap_pager: indefinite wait buffer - on 5.3-RELEASE-p5

From: Oliver Fromme (olli_at_lurza.secnetix.de)
Date: 04/29/05

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    Date: Fri, 29 Apr 2005 14:13:25 +0200 (CEST)
    To: freebsd-stable@FreeBSD.ORG, tssajo@hotmail.com
    
    

    Zoltan Frombach <tssajo@hotmail.com> wrote:
    > Apr 29 02:10:14 www kernel: swap_pager: indefinite wait buffer: device:
    > ad0s1a, blkno: 328636, size: 8192
    > Apr 29 02:10:24 www kernel: swap_pager: indefinite wait buffer: device:
    > ad0s1e, blkno: 329842, size: 4096
    > [...]

    The error message indicates that there was an I/O error
    accessing the swap area on your disk. Usually that's an
    indication for a hardware failure, e.g. a dying disk.

    > I happen to have an identical hard drive around here, unused. If I hook it
    > up as a slave (IDE) drive, is there a way I can mirror the dying drive to
    > the spare one (with all partitions, etc, intact)?

    If they're really identical (i.e. the same size and same
    geometry), then you can use dd(1) for duplication, like
    this:

    # dd if=/dev/ad0 of=/dev/ad1 bs=64k conv=noerror,sync

    The "noerror,sync" part is important so the dd command will
    not stop when it hits any bad spots on the source drive and
    instead will fill the blocks with zeroes on the destination
    drive. Since it's only the swap partition, you shouldn't
    lose any data.

    However, one disadvantage of dd is that it copies the drive
    on block level, which means that it will also copy empty
    blocks which aren't used at all. Neither does it make
    sense to copy the swap partition.

    If the filesystems on that drive don't contain much data,
    it might be mor efficient to copy the data on filesystem
    level. To do that, copy just the boot sector and disklabel
    (using dd(1) to copy the first 64k or something should be
    sufficient), then newfs the filesystems, mount them and
    copy the contents with an appropriate tool. I recommend
    "cpdup" from the port collection, because it's fast and
    easy to use, but cpio should work as well (and it's in the
    base of pretty much every UNIX system).

    Performing newfs + filesystem copy also has the advantage
    that you're starting with fresh, unfragmented filesystems,
    and it gives you the opportunity to finetune the parameters
    if necessary, such as the inode density (newfs -i).

    > Any help/comments would be appreciated. Please CC me, as I am not a
    > subscriber of this list. Thanks!!!

    In that case you should set the "Reply-To" header in your
    mail appropriately.

    Best regards
       Oliver

    -- 
    Oliver Fromme, secnetix GmbH & Co KG, Oettingenstr. 2, 80538 München
    Any opinions expressed in this message may be personal to the author
    and may not necessarily reflect the opinions of secnetix in any way.
    "In My Egoistical Opinion, most people's C programs should be indented
    six feet downward and covered with dirt."
            -- Blair P. Houghton
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