PVs may also be organized into "physical volume groups" or PVGs. This allows LVs to be mirrored by pairing together its PEs with redundant ones on a different PVG, so that the failure of one PVG will still leave at least one complete copy of the LV online. In practice, PVGs are usually chosen so that their PVs are on different sets of disks and/or data buses for maximum redundancy.