Well, I wouldn't use it, but there were one or two people who were interested in mirroring, and I offered to try to get it working because I wanted to work on something.

Unfortunately, I don't believe that Linux RAID can run half a RAID mirror without going through the RAID driver because it stores metadata in the actual partition rather than out of band, like, for example, Solaris RAIDs.

And the reason that the RAID needs to be on all partitions is because if a drive were to fail, then the root partition could go away, which makes the fact that the music is still there irrelevant, as the requester's point was that it would suck to be on a trip and have the empeg go tits up.