Never tried it with raq's, but I don't see why it wouldn't work there as well. The tricky part is keeping the data in sync, but depending on your needs, you can use things such as rsync, mysql server replication, or nfs.
Alex could you please elaborate on how you perform MySQL server replication ? Or please point me to a resource which explains how to do it in more detail ? I've been looking for an effective way to do this for a wee while now :-) Thanks ! Kam.