Journal-guided RAID resync
Posted Nov 26, 2009 20:54 UTC (Thu) by neilbrown
In reply to: Journal-guided RAID resync
Parent article: Journal-guided RAID resync
Hang on. If you crash after a RAID-5 stripe has been written to one of the
disks but not the other, you can tell the stripe is inconsistent, but not
what the valid contents are (at least, not programmatically.)
Between the moment when a write is requested, and the moment when the success of that write is reported - and possibly further until a barrier request has been acknowledged - both the 'old' data and the 'new' data are valid. The correct thing to do in this case is to treat all of the data blocks as "valid" (because they are) and update the parity block to ensure it is consistent.
What do you think "Valid" means in this context?
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