Raid-1 to Raid-5 conversion possible?

Raid-1 to Raid-5 conversion possible?

[Vidar Sonerud]

I have for a long time been wondering if it is possible to convert a 2
disk Raid-1 array to a  3 disk Raid-5 array using mdadm?

Tonight I stumbled upon this article:

http://www.n8gray.org/blog/2006/09/05/stupid-raid-tricks-with-evms-and-mdadm/

Is this safe / ok to do? Any comments from you mdadm experts?

Best regards
Vidar Sonerud

Re: Raid-1 to Raid-5 conversion possible?

[Neil Brown]

On Wednesday January 24, vidar.sonerud@gmail.com wrote:
> I have for a long time been wondering if it is possible to convert a 2
> disk Raid-1 array to a  3 disk Raid-5 array using mdadm?
> 
> Tonight I stumbled upon this article:
> 
> http://www.n8gray.org/blog/2006/09/05/stupid-raid-tricks-with-evms-and-mdadm/
> 
> Is this safe / ok to do? Any comments from you mdadm experts?

Yes, that should be safe - in principle.
I've never used EVMS tools so I cannot comment on the particular
commands that the article says to run.

I would do it with mdadm:

1/ stop the array
   mdadm -S /dev/md0
2/ Recreated as a RAID5 array
   mdadm -C /dev/md0 -l5 -n2 --assume-clean /dev/sda1 /dev/sdb1
3/ Add a spare
   mdadm /dev/md0 -a /dev/sdc1
4/ Grow the array
   mdadm -G /dev/md0 -n 3

all done.

Of course you have to change the device names to fit your hardware.

NeilBrown