Ricardo Correia has been porting Sun’s recently GPLed ZFS to Linux using FUSE. I’ve been playing with it and I’m quite impressed. The FUSE port is alpha quality, so isn’t to be trusted with important data yet – but it’s fun to play with.
ZFS merges the concept of a volume manager and a filesystem. It’s a bit like LVM, with zpools being volume groups and zfs being formatted logical volumes. Zfs “partitions” can change size at any time in any way. It’s also hierarchical, so zfs partitions can have child partitions inheriting their attributes. It also does away with fstab – all mount points are specified as zfs attributes and are automatically mounted when a zpool is brought online.