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    SubjectRe: [PATCH] md: Add support for data integrity to MD
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    >>>>> "Dan" == Dan Williams <dan.j.williams@gmail.com> writes:

    >> + /* Data integrity passthrough not supported on RAID 4, 5 and 6 */
    >> + if (pers->level >= 4 && pers->level <= 6) + return 0;

    Dan> Do you have a reference to the issues in supporting this?

    Not really.

    The protection information is an extra 8-bytes of stuff per sector.
    But it comes down in a different buffer. To do R-M-W effectively
    we'll have to maintain a separate protection information stripe cache.
    And we'll have to generate DIF checksums and reference tags for the
    parity sectors going out.

    Quite frankly it's a lot of ick and I haven't completely wrapped my
    head around it yet.

    --
    Martin K. Petersen Oracle Linux Engineering



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