On 7/23/07, Neil Brown <neilb@xxxxxxx> wrote:
On Saturday July 21, snitzer@xxxxxxxxx wrote:
> Could you share the other situations where a bitmap-enabled raid1 > _must_ perform a full recovery? When you add a new drive. When you create a new bitmap. I think that should be all. > - Correct me if I'm wrong, but one that comes to mind is when a server > reboots (after cleanly stopping a raid1 array that had a faulty > member) and then either: > 1) assembles the array with the previously faulty member now > available > > 2) assembles the array with the same faulty member missing. The user > later re-adds the faulty member > > AFAIK both scenarios would bring about a full resync. Only if the drive is not recognised as the original member. Can you test this out and report a sequence of events that causes a full resync?
Sure, using an internal-bitmap-enabled raid1 with 2 loopback devices on a stock 2.6.20.1 kernel, the following sequences result in a full resync. (FYI, I'm fairly certain I've seen this same behavior on 2.6.18 and 2.6.15 kernels too but would need to retest): 1) mdadm /dev/md0 --manage --fail /dev/loop0 mdadm -S /dev/md0 mdadm --assemble /dev/md0 /dev/loop0 /dev/loop1 mdadm: /dev/md0 has been started with 1 drive (out of 2). NOTE: kernel log says: md: kicking non-fresh loop0 from array! mdadm /dev/md0 --manage --re-add /dev/loop0 2) mdadm /dev/md0 --manage --fail /dev/loop0 mdadm /dev/md0 --manage --remove /dev/loop0 mdadm -S /dev/md0 mdadm --assemble /dev/md0 /dev/loop0 /dev/loop1 mdadm: /dev/md0 has been started with 1 drive (out of 2). NOTE: kernel log says: md: kicking non-fresh loop0 from array! mdadm /dev/md0 --manage --re-add /dev/loop0 Is stopping the MD (either with mdadm -S or a server reboot) tainting that faulty member's ability to come back in using a quick bitmap-based resync? Mike - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
