Re: "bitmap file is out of date, doing full recovery"

[NeilBrown <neilb@suse.de>]

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On Sun, 12 Oct 2014 21:03:57 +0300 Alexander Lyakas <alex.bolshoy@gmail.com>
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 md24: bitmap file is out of date (41 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 md24: bitmap file is out of date, doing full recovery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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