Re: Rotating RAID 1

[maurice <mhilarius@gmail.com>]

On 8/15/2011 4:42 PM, NeilBrown wrote:
> ..I'm not sure from you description whether the following describes 
> exactly
> what you are doing or not, but this is how I would do it.
> As you say, you need two bitmaps.
> So if there are 3 drives A, X, Y where A is permanent and X and Y are 
> rotated off-site,
> then I create two RAID1s like this:
>   mdadm -C /dev/md0 -l1 -n2 --bitmap=internal /dev/A /dev/X
>   mdadm -C /dev/md1 -l1 -n2 --bitmap=internal /dev/md0 /dev/Y
>
>   mkfs /dev/md1; mount /dev/md1 ...
>
> Then you can remove either or both of X and Y and which each is 
> re-added it will
> recover just the blocks that it needs.
> X from the bitmap of md0, Y from the bitmap of md1.
>
> NeilBrown


How elegantly described.

After so many instances of being told "You should not use RAID as a 
backup device like that!"
it is pleasant to hear you detail the "right way" to do this.

Thank you very much for that Neil.


-- 
Cheers,
Maurice Hilarius
eMail: /mhilarius@gmail.com/