Re: Raid 1 Issues

[Neil Brown]

On Friday September 13, [e-mail] 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