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    SubjectRe: raid 1 - automatic 'repair' possible?
    On Wed, Jan 19, 2005 at 11:48:52AM +0100, Kiniger wrote:
    > some random thoughts:
    > nowadays hardware sector sizes are much bigger than 512 bytes

    No :)

    > and
    > the read error may affect some sectors +- the sector which actually
    > returned the error.

    That's right

    > to keep the handling in userspace as much as possible:
    > the real problem is the long resync time. therefore it would
    > be sufficient to have a concept of "defective areas" per partition
    > and drive (a few of them, perhaps four or so , would be enough)
    > which will be excluded from reads/writes and some means to
    > re-synchronize these "defective areas" from the good counterparts
    > of the other disk. This would avoid having the whole partition being
    > marked as defective.

    I wonder if it's really worth it.

    The original idea has some merit I think - but what you're suggesting
    here is almost "bad block remapping" with transparent recovery and user
    space policy agents etc. etc.

    If a drive has problems reading the platter, it can usually be corrected
    by overwriting the given sector (either the drive can actually overwrite
    the sector in place, or it will re-allocate it with severe read
    performance penalties following). But there's a reason why that sector
    went bad, and you realy want to get the disk replaced.

    I think the current policy of marking the disk as failed when it has
    failed is sensible.

    Just my 0.02 Euro


    / jakob

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