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    SubjectRe: Strange messages in my kernel log
    On Thu, 31 Aug 2000, Neil Brown wrote:

    >On Wednesday August 30, avn@spylog.com wrote:
    >>
    >> I have strange messages in my kernel log (1-2 messages per day)
    >>
    >> raid5: bug: stripe->bh_new[2], sector 477640 exists
    >> raid5: bh 8ffd6da0, bh_new 8ffd63e0
    >> raid5: bug: stripe->bh_new[2], sector 6677320 exists
    >> raid5: bh aca1f060, bh_new aca1f720
    >> raid5: bug: stripe->bh_new[1], sector 6854048 exists
    >> raid5: bh b94c02c0, bh_new b94c0260
    >> raid5: bug: stripe->bh_new[2], sector 6889584 exists
    >> raid5: bh 833949c0, bh_new 83394d80
    >>
    >>
    >> What does it mean? Can this cause data corruption? Can i fix this problem?
    >> I use softvare RAID level 5, in kernel 2.2.16 with RH patches.
    >
    >What does it means?
    >
    > It means that raid5 received an IO request for a block of data for
    > which is already had an outstanding IO request. In these cases the
    > two i/o requests had different buffer_head strutures.
    > raid5 reports a bug, but actually handles the situation fairly
    > gracefully: it blocks the second request until the first has
    > finished.
    >
    >Can this cause data corruption?
    >
    > Not directly, but it might be a symptom of something else that could
    > cause corruption.
    >
    >Can i fix this problem?
    >
    > Maybe, but first we need to understand it.
    > The question is, how could there be two different buffer_heads for
    > the same block on disk?
    > My understanding of the 2.2 buffer cache is not very good, but I
    > think that all filesystems and block device IO go through the buffer
    > cache, so any of these accesses should never allow two buffer_heads
    > to point to the same block.
    > However I believe that swapping doesn't go through the buffer cache.
    >
    > So: what are you doing with the raid5 partition.
    > What sort of file system?
    Ext2fs with strige=16

    > Are you swapping to a file on the filesystems?
    No I have BIG MySQL database on this FS

    > Is there any chance that a parity reconstruction is happening when
    > you get these messages.
    Hmm... Parity reconstuction was complete before i put any data to new
    array. I not seen messages about another reconstruction.

    > Is there anything at all about your usage of the raid5 device that
    > could possibly be at all out of the ordinary?
    >

    >> Also I have second question.
    >> How much stable software RAID in latset 2.4.0 test series?
    >
    >quite stable, but not very fast. RAID5 in 2.4.0 in particular is much
    >slower than 2.2.xx with mingo's patches. I'm working on this from
    >time to time.
    Can I upgrade kernel without rebuild/reformat array?

    --
    With best regards
    Alexander V. Nikolaev
    System administrator of spylog.com

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