Lost my RAID

[Paul Howarth]

Martin Marques wrote:
> I have a Linux RAID1 on 2 SATA disks on a FC4. The problem is that we had issues with the disks (power cables had trouble) and now one of the disks gets kicked out of the RAID:
> 
> md: raid1 personality registered for level 1
> md: Autodetecting RAID arrays.
> md: autorun ...
> md: considering sdb1 ...
> md:  adding sdb1 ...
> md:  adding sda1 ...
> md: created md0
> md: bind<sda1>
> md: bind<sdb1>
> md: running: <sdb1><sda1>
> md: kicking non-fresh sdb1 from array!
> md: unbind<sdb1>
> md: export_rdev(sdb1)
> raid1: raid set md0 active with 1 out of 2 mirrors
> md: ... autorun DONE.
> 
> And later in the boot I have this:
> 
> md: Autodetecting RAID arrays.
> md: autorun ...
> md: considering sdb1 ...
> md:  adding sdb1 ...
> md: md0 already running, cannot run sdb1
> md: export_rdev(sdb1)
> md: ... autorun DONE.
> 
> Someone told me I would have to rebuild the array with mdadm, but I want to know if I would loose data doing so.

You should just be able to re-add sdb1 to the array and it'll rebuild in 
the background. No data loss.

Try checking the status of the array:
# mdadm --detail /dev/md0

If it just shows sda1, you can add sdb1 back in straight away:
# mdadm /dev/md0 -a /dev/sdb1

If it shows sdb1 as still being part of the array, you'll need to remove 
it first and then re-add it:
# mdadm /dev/md0 -r /dev/sdb1
# mdadm /dev/md0 -a /dev/sdb1

You can then re-check the status and see sdb1 getting rebuilt:
# mdadm --detail /dev/md0

Paul.