On Tue, Oct 21, 2008 at 09:38:17AM +0100, David Greaves wrote:
The main issue is that the drive being replaced almost certainly has a bad
block. This block could be recovered from the raid5 set but won't be.
Worse, the mirror operation may just fail to mirror that block - leaving it
'random' and thus corrupt the set when replaced.
False,
if SMART reports the drive is failing, it just means the number of
_correctable_ errors got too high, remember that hard drives (*) do use
ECC and autonomously remap bad blocks.
You replace a drive based on smart to prevent it developing bad blocks.
Ignoring the above, your scenario is still impossible, if you tried to
mirror a source drive with a bad block, md will notice and fail the
mirroring process. You will never end up with one drive with a bad block
and the other with uninitialized data.
If what you are really worried about is not bad block, but silent
corruption, you should run a check (see sync_action in
/usr/src/linux/Documentation/md.txt)
L.
(*) note that i don't write 'modern hard drives'.
--
Luca Berra -- bluca@xxxxxxxxxx
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