On Sun, 12 Oct 2014 21:03:57 +0300 Alexander Lyakas <alex.bolshoy@xxxxxxxxx> wrote: > Hi Neil, > after a 2-drive raid1 unclean shutdown (crash actually), after reboot, we had: > > md/raid1:md24: not clean -- starting background reconstruction > md/raid1:md24: active with 2 out of 2 mirrors > md24: bitmap file is out of date (41 < 42) -- forcing full recovery > created bitmap (22 pages) for device md24 > md24: bitmap file is out of date, doing full recovery > md24: bitmap initialized from disk: read 2 pages, set 44667 of 44667 bits > > The superblock of both drives had event count = 42: > (this is a custom mdadm with some added prints): > mdadm: looking for devices for /dev/md24 > mdadm: [/dev/md24] /dev/dm-205: slot=0, events=42, > recovery_offset=N/A, resync_offset=0, comp_size=5854539776 > mdadm: [/dev/md24] /dev/dm-206: slot=1, events=42, > recovery_offset=N/A, resync_offset=0, comp_size=5854539776 > > But the bitmap superblock had lower event count, which resulted in a > full resync. Is this an expected scenario in case of a crash? No. > > For example in md_update_sb, first we call > bitmap_update_sb(mddev->bitmap), which synchronously updates the > bitmap, and only afterwards we go ahead and update our superblocks. So > in this case, the bitmap should not have a lower event count. Is there > some other valid scenario, in which the bitmap can remain with a lower > event count? Not that I can think of. NeilBrown > > Thanks, > Alex.
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