On 22/11/13 23:59, NeilBrown wrote:
On Fri, 22 Nov 2013 10:07:09 -0600 Stan Hoeppner <stan@xxxxxxxxxxxxxxxxx>
wrote:
<snip>
In the event of a double drive failure in one mirror, the RAID 1 code
will need to be modified in such a way as to allow the RAID 5 code to
rebuild the first replacement disk, because the RAID 1 device is still
in a failed state. Once this rebuild is complete, the RAID 1 code will
need to switch the state to degraded, and then do its standard rebuild
routine for the 2nd replacement drive.
Or, with some (likely major) hacking it should be possible to rebuild
both drives simultaneously for no loss of throughput or additional
elapsed time on the RAID 5 rebuild.
Nah, that would be minor hacking. Just recreate the RAID1 in a state that is
not-insync, but with automatic-resync disabled.
Then as continuous writes arrive, move the "recovery_cp" variable forward
towards the end of the array. When it reaches the end we can safely mark the
whole array as 'in-sync' and forget about diabling auto-resync.
NeilBrown
That was my thoughts here. I don't know what state the planned "bitmap
of non-sync regions" feature is in, but if and when it is implemented,
you would just create the replacement raid1 pair without any
synchronisation. Any writes to the pair (such as during a raid5
rebuild) would get written to both disks at the same time.
David
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