Re: Raid 1 Issues

Neil Brown (neilb@cse.unsw.edu.au)
Tue, 17 Sep 2002 09:41:10 +1000


On Friday September 13, lsawyer@gci.com wrote:
> I'm running 2.4.18, and trying to use Raid-1.
>
> I created /etc/raidtab according to the instructions.
> raiddev /dev/md0
> raid-level 1
> nr-raid-disks 2
> nr-spare-disks 0
> device /dev/hdc2
> raid-disk 0
> device /dev/hdb2
> raid-disk 1
>
SNIP
> "cat /proc/mdstat" shows the the devices connected, but not attached:
>
> Personalities : [raid1]
> read_ahead 1024 sectors
> md0 : active raid1 ide/host0/bus0/target1/lun0/part2[1]
> ide/host0/bus1/target0/lun0/part2[0]
> 77914752 blocks [1/1] [U]
> unused devices: <none>
>

There is an inconsistancy here. Your raidtab says "nr-raid-disks 2",
but mdstat shows there is only 1 raid-disk in the array.

You will need to recreate the array using "mkraid -R /dev/md0"
with a raidtab of
> raiddev /dev/md0
> raid-level 1
> nr-raid-disks 2
> device /dev/hdc2
> raid-disk 0
> device /dev/hdb2
> failed-disk 1

or with
mdadm -C /dev/md0 --level=1 -n 2 /dev/hdc2 missing

Then "raidhotadd /dev/md0 /dev/hdb2" or "mdadm /dev/md0 -a /dev/hdb2"
should add the other drive in.
Ofcourse you will need to unmount /usr and "raidstop -a" or "mdadm -Ss"
first.

mdadm is available at
http://www.cse.unsw.edu.au/~neilb/source/mdadm/

NeilBrown
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