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    SubjectRe: RAID-5 design bug (or misfeature)
    Mikulas Patocka wrote:
    > RAID-5 has rather serious design bug --- when two disks become temporarily
    > inaccessible (as it happened to me because of high temperature in server
    > room), linux writes information about these errors to the remaining disks
    > and when failed disks are on line again, RAID-5 won't ever be accessible.

    I ran into this myself, however, I had 10 disks (5 per channel) and one
    chennel went down. Ok, my array was dead at that point and I had to reboot.
    What luck, the arry wasn't usable anymore. My /usr was on that array, but
    my / was not. I did not want to go through the initrd/initramfs thing at
    the time to setup my / with raid5, plus the fact you truely cannot boot from
    it (thus partitioning and setting aside a slice wasn't viable to me)

    > RAID-HOWTO lists some actions that can be done in this case, but none of
    > them can be done if root filesystem is on RAID --- the machine just won't
    > boot.

    I had to reconstruct the array by hand with mdadm. evms wouldn't touch it.
    Fortunately, I had a copy of each disk's information and the raid5's
    information in files so it was quite easy to rebuild. I did have backups
    but that wasn't really what I wanted to do. (It did take over 2 hours
    before I could return to normal. evms can't handle a raid5 that was in
    reconstruction. I think newer versions have this fixed.)

    > I think Linux should stop accessing all disks in RAID-5 array if two disks
    > fail and not write "this array is dead" in superblocks on remaining disks,
    > efficiently destroying the whole array.

    That'd be nice =)

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