[CentOS] adding a usb drive to an existing raid1 set

Les Mikesell lesmikesell at gmail.com
Fri Sep 29 01:36:53 UTC 2006

On Thu, 2006-09-28 at 18:16, rado wrote:

> kk...the ide drives; hda and hdc...3 partitions 3 arrays md0 1 and 2 
> cat /proc/mdstat shows it's acting as it should.

Are you trying to add a 3rd partition to a raid created with only
2?  I don't think that will work, although you could fail/remove
an existing partition, then add the new one as a replacement.

> when I boot the system up, it sees the drive connect thru usb and calls
> it sda (for what reason I don't know. I partitioned it to the same specs
> as the 2 ide drives as per the bottom of fdisk -l. 

USB/firewire drives are assigned the next available scsi device
name as detected - doesn't make much sense to me either...

> ummm...1.)I think this is part of the old raidtools thang...not mdadm
> but I am not sure.
> 	2.) there is no man raidtab on this box which is a "everything"
> install..

Raidtab isn't used any more - it's all mdadm commands.

> kk, right now...I just formatted all the partitions and (I should have
> done this before ) I am checking for bad blocks. If it finds some I'll
> just redo it or whatever I have to do. At one point I was able to
> mdadm /dev/md0 1 & 2 --add sda1 2 &3 and 
> cat /proc/mdstat would show sda1 2 &3 as in the arrays but then they
> would not populate.

It's only going to rebuild the number of devices you gave
in the create command (or whever disk druid set up if you
did it that way).  I'm not sure if there is any way to change
that later.

  Les Mikesell
   lesmikesell at gmail.com

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