Chiron FS is a FUSE based filesystem which implements replication at the
FILESYSTEM LEVEL like RAID 1 does at the DEVICE LEVEL. The replicated
filesystems may be of any kind you want the only requisite is that you
mount it. No need for special configuration files, the setup is as simple
as one mount command (or one line in fstab).

WWW:    http://code.google.com/p/chironfs/