On Sat, 14 Feb 2015 21:59:34 +0000 (UTC) Chris <email.bug@xxxxxxxx> wrote: > > Hi all, > > I'd like mdadm to automatically attempt to re-sync raid members after they > where temporarily removed from the system. > > I would have thought "POLICY domain=default action=re-add" should allow this, > and found a prior post that also seemed to want/test that behaviour. > But as I understand the answer given there > http://permalink.gmane.org/gmane.linux.raid/47516 > mdadm is expected to exit with an error (not re-add) upon plugging the > device back in? > > with: > mdadm: can only add /dev/loop2 to /dev/md0 as a spare, and force-spare is > not set. > mdadm: failed to add /dev/loop2 to existing array /dev/md0: Invalid argument. > > For one, I don't understand what the error messages is trying to tell me, about > an invalid argument that was never supplied to --incremental? > > But more importantly, how can priorly diconnected devices (marked failed > with non-future event count) get re-synced automatically when they are > plugged in again? > (avoiding manual mdadm /dev/mdX --add /dev/sdYZ hassle) > Does your array have a write-intent bitmap configured? If it does, then "POLICY action=re-add" really should work. If it doesn't, then maybe you need "POLICY action=spare". This isn't the default, because depending on exactly how/why the device failed, it may not be safe to treat it as a spare. If the above does not help, please report: - kernel version - mdadm version - "mdadm --examine" output of at least one good drive and one failed drive. NeilBrown
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