----- Original Message -----
From: "Luca Berra" <bluca@xxxxxxxxxx>
To: <linux-raid@xxxxxxxxxxxxxxx>
Sent: Friday, April 23, 2010 8:51 AM
Subject: Re: Suggestion needed for fixing RAID6
On Thu, Apr 22, 2010 at 12:09:08PM +0200, Janos Haar wrote:
Hello Neil, list,
I am trying to fix one RAID6 array wich have 12x1.5TB (samsung) drives.
Actually the array have 1 missing drive, and 3 wich have some bad
sectors!
Genearlly because it is RAID6 there is no data lost, because the bad
sectors are not in one address line, but i can't rebuild the missing
drive, because the kernel drops out the bad sector-drives one by one
during the rebuild process.
I would seriously consider moving the data out of that array and dumping
all drives from that batch, and this is gonna be painful because you
must watch drives being dropped and add them back, and yes you need the
resources to store the data.
ddrescue won't obviously work, since it will mask read errors and turn
those into data corruption
the raid 1 trick wont work, as you noted
another option could be using the device mapper snapshot-merge target
(writable snapshot), which iirc is a 2.6.33+ feature
look at
http://smorgasbord.gavagai.nl/2010/03/online-merging-of-cow-volumes-with-dm-snapshot/
for hints.
btw i have no clue how the scsi error will travel thru the dm layer.
L.
...or cowloop! :-)
This is a good idea! :-)
Thank you.
I have another one:
re-create the array (--assume-clean) with external bitmap, than drop the
missing drive.
Than manually manipulate the bitmap file to re-sync only the last 10% wich
is good enough for me...
Thanks again,
Janos
--
Luca Berra -- bluca@xxxxxxxxxx
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