Re: Raid 6 rebuild

[NeilBrown <neilb@suse.de>]

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On Fri, 6 Apr 2012 03:01:26 -0400 Bryan Bush <bbushvt@gmail.com> wrote:

> If you have 2 failed drives in a raid 6 array, will it rebuild them
> both at the same time or in serial?

Maybe.

Probably not, but it can be coaxed to.

The next release of mdadm will contain

http://neil.brown.name/git?p=mdadm;a=commitdiff;h=9f58469128c99c0d7f434d28657f86789334f253

which will ensure that if you:

  mdadm /dev/md0 --add /dev/foo /dev/bar

then both will be added before the recovery starts, so both will be recovered
at the same time.

Alternately you could:

 echo freeze > /sys/block/md0/md/sync_action
 mdadm /dev/md0 --add /dev/foo /dev/bar
 echo idle > /sys/blcok/md0/md/sync_action

you might even be able to leave of the first step.
The "add" will cause a recovery to start on just one device, but then when
you write 'idle', it will abort  the recovery, automatically restart, but
this time will use all available spares.

NeilBrown


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