> What you could do is set the number of devices in the array to 3 so
> they it always appears to be degraded, then rotate your backup drives
> through the array.  The number of dirty bits in the bitmap will
> steadily grow and so resyncs will take longer.  Once it crosses some
> threshold you set the array back to having 2 devices to that it looks
> non-degraded and clean the bitmap.  Then each device will need a full
> resync after which you will get away with partial resyncs for a while.

I don't undertand why clearing the bitmap causes a rebuild of
all devices. I think I have a conceptual misunderstanding.  Consider
a RAID-1 and three physical disks involved, A,B,C

1) A and B are in the RAID, everything is synced
2) Create a bitmap on the array
3) Fail + remove B
4) Hot add C, wait for C to sync
5) Fail + remove C
6) Hot add B, wait for B to resync
7) Goto step 3

I understand that after a while we might want to clean the bitmap
and that would trigger a full resync for drives B and C. I don't
understand why it would ever cause a resync for drive A.
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