Half a Mirror Backup

[David Brodbeck]

On Sun, Jan 2, 2011 at 11:56 AM, Jason C. Wells <jcw at speakeasy.net> wrote:
> Is using one half of a mirror as a backup a good/bad idea?
>
> I was thinking of rotating drives on a periodic basis as a back up method.
>  You'd get the backup instantly, but rebuilding the mirror with the incoming
> drive would take a little time and leave you vulnerable to a small loss of
> data if a disk failed while the mirror was rebuilding.

Besides the problem you mention, you'll have a pretty sizable
performance hit while the mirror is being rebuilt.  Also, keep in mind
that the most likely time for a second drive to fail is during a
rebuild, since the rebuild forces a read from every sector.  I think I
would use rsync or dump instead, although I have to admit the rotating
mirror idea is clever.