Another RAID level migration question

Another RAID level migration question

[Bill Davidsen]

I have an array on two drives which was set up as a RAID-0, because I 
needed the space and performance. Now I have another identical drive, 
ideally I would like to get to RAID-5, but I don't think that is going 
to fly, so how about RAID-4? I could create with a missing parity drive, 
then add the drive and see if it will rebuild.

I hope to test this using loop devices, but time is fairly short right now.

-- 
bill davidsen <davidsen@tmr.com>
  CTO TMR Associates, Inc
  Doing interesting things with small computers since 1979

Re: Another RAID level migration question

[Neil Brown]

On Thursday August 9, davidsen@tmr.com wrote:
> I have an array on two drives which was set up as a RAID-0, because I 
> needed the space and performance. Now I have another identical drive, 
> ideally I would like to get to RAID-5, but I don't think that is going 
> to fly, so how about RAID-4? I could create with a missing parity drive, 
> then add the drive and see if it will rebuild.
> 
> I hope to test this using loop devices, but time is fairly short right now.

Providing the two drives are exactly the same size (which rounded down
to a multiple of 64K), this  will work.  The parity drive is the last
in the list so
   mdadm -C /dev/mdX -l4 -n3 -c WHATEVER /dev/sda1 /dev/sdb1 missing

is the sort of thing you want.

NeilBrown