Messages in this thread | | | Subject | Re: [PATCH] md: Add support for data integrity to MD | From | "Martin K. Petersen" <> | Date | Sat, 20 Sep 2008 22:01:29 -0400 |
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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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