Re: modifying degraded raid 1 then re-adding other members is bad

On Tuesday August 8, khc@pm.waw.pl wrote:

Michael Tokarev [off-list ref] writes:

quoted

Why we're updating it BACKWARD in the first place?

Another scenario: 1 disk (of 2) is removed, another is added, RAID-1
is rebuilt, then the disk added last is removed and replaced by
the disk which was removed first. Would it trigger this problem?

No.  The removing and the adding will all move the event count clearly
forward and the removed drive will have an old event count and so will
not be considered for easy inclusion.

quoted

Also, why, when we adding something to the array, the event counter is
checked -- should it resync regardless?

I think it's a full start, not a hot add. For hot add contents of
the new disk should be ignored.

See my other post for why I want to sometimes not do a recovery on a
hot-add.

NeilBrown