metadevice -- A group of physical slices accessed as a single logical device by RAID 0 concatenations, RAID 0 (stripe) volumes, RAID 1 (mirror) volumes, RAID 5 volumes, or logging physical devices. After they are created, metadevices are used like slices.
The metadevice maps logical block addresses to the correct location on one of the physical devices. The type of mapping depends on the configuration of the particular metadevice.
Also known as pseudo, or virtual device in standard UNIX terms.