[linux-lvm] [LVM/RAID BUG DATA DESTRUCTION] 3.12.14 raid1 initialisation + --write-mostly destroys LV

[David Lamparter]

On Wed, Apr 02, 2014 at 02:03:21PM +0200, David Lamparter wrote:
> lvconvert --type raid1 -m 1 eidolon/root
> lvchange --writemostly /dev/sda4:y --writebehind 32768 eidolon/root
[...]
> The raid1 was still initialising (around 20%) when I executed the second
> command, output from /sys/block/*/stat leads me to believe the sync direction
> was inverted from the newly-added device to the existing one.
[...]
> [950580.682165] mdX: bitmap initialized from disk: read 4 pages, set 98948 of 122880 bits

A quick disk inspection with dd/hexdump indicates that garbage starts
around 19.5%, which lines up with "98948 of 122880" above.


-David