On Wed, May 20, 2015 at 04:20:49PM +0200, Jan Kasprzak wrote:
> Hello,
Hi Jan,
>
> I have a RAID-5 volume of 8 physical disks. One of these disks failed the SMART
> self-test with an unreadable block error. Unfortunately I have discovered
> that there is _another_ bad block on another disk. It is a different block,
> so the RAID-5 volume as a whole is still working. But as a whole, the
> RAID-5 volume has at least two unreadable sectors on two different disks.
>
> What is the best way to replace these two failing disks one by one without
> the loss of data? I cannot mdadm --fail one of them, because the
> subsequent rebuild on a new disk would fail on reading the other bad block.
>
> I would like to add the ninth drive to the RAID-5 volume, and put a replica
> of one of the failing drives to it. Then remove the just-replicated drive,
> and do the same with the other failing drive.
When you take a look in mdadm man page and search for --replace you'll find what you are looking for.
--replace
Mark listed devices as requiring replacement. As soon as a spare is available, it will be rebuilt and will replace
the marked device. This is similar to marking a device as faulty, but the device remains in service during the recov-
ery process to increase resilience against multiple failures. When the replacement process finishes, the replaced
device will be marked as faulty.
--with This can follow a list of --replace devices. The devices listed after --with will be preferentially used to replace
the devices listed after --replace. These device must already be spare devices in the array.
HTH,
/lm
>
> Thanks,
>
> -Yenya
>
> --
> | Jan "Yenya" Kasprzak <kas at {fi.muni.cz - work | yenya.net - private}> |
> | New GPG 4096R/A45477D5 -- see http://www.fi.muni.cz/~kas/pgp-rollover.txt |
> | http://www.fi.muni.cz/~kas/ Journal: http://www.fi.muni.cz/~kas/blog/ |
> Smart data structures and dumb code works a lot better
> than the other way around. --Eric S. Raymond
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