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    SubjectRe: ATA 4 KiB sector issues.
    Dave Chinner wrote:
    > On Tue, Mar 09, 2010 at 01:16:01PM +0300, Michael Tokarev wrote:
    >> Karel Zak wrote:
    >>> I did almost all my tests with scsi_debug or MD RAID0 on scsi_debug.
    >>> It works as expected.
    >> Actually, for raid0, the alignment is questionable. Should it be a
    >> multiple of chunk size or whole stripe size? I'm not sure, both ways
    >> has bad and good sides.. But if it is the latter, the same issues
    >> pops up again: do a 3-disk raid0 and you'll have to align to 3*2^N.
    >
    > Yes, alignment is still needed, especially for filesystems that can
    > do stripe unit aligned allocation like XFS. If you don't align the
    > filesystem properly, all the data IO will be mis-aligned to the
    > underlying disks and stripe unit sized IO will hit multiple disks
    > rather than just one....

    I understand alignment is needed, the question is if the alignment
    should be to chunk size or full-stripe size. In neither case it
    will be bad for underlying disks.

    /mjt


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