A RAID1 device does not necessarily need a fullsync if the bitmap can be used instead. Similar to commit d6b212f4b19da5301e6b6eca562e5c7a2a6e8c8d in raid5.c, if a raid1 device can be brought back (i.e. from a transient failure) it shouldn't need a complete resync. Provided the bitmap is not to old, it will have recorded the areas of the disk that need recovery. ** I've used 'saved_raid_disk' here similar to RAID5, but it doesn't seem to fit as well. The positions aren't really as important as they are in RAID5, and I'm using the 'saved_raid_disk' as more of an indicator that it can use the bitmap, rather than for any other purpose. Perhaps the meaning is being overloaded and a different solution should be found? RFC-by: Jonathan Brassow <jbrassow@xxxxxxxxxx> Index: linux-upstream/drivers/md/raid1.c =================================================================== --- linux-upstream.orig/drivers/md/raid1.c +++ linux-upstream/drivers/md/raid1.c @@ -2597,7 +2597,8 @@ static struct r1conf *setup_conf(struct if (!disk->rdev || !test_bit(In_sync, &disk->rdev->flags)) { disk->head_position = 0; - if (disk->rdev) + if (disk->rdev && + (disk->rdev->saved_raid_disk != disk->rdev->raid_disk)) conf->fullsync = 1; } else if (conf->last_used < 0) /* -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel