ZFS is a free, open-source file system developed by Sun Microsystems for its Solaris operating system. The freeware is noted for its high capacity, integration of the concepts of filesystem and volume management, novel on-disk structure, lightweight filesystems, and easy storage pool management. 

Or you can go by Sun's one liner description of their product, "ZFS, The Last Word In Filesystems."

The Apple tree, where rumors about Apple sprout and wither, is still buzzing over the news that the Mac OS X system, is looking to adopt ZFS. It's one of those things that Apple People would love to crunch their teeth on. Yes, it's still unconfirmed but that didn't stop StorageMojo from conjuring a scenario where MacLeopards are born with ZFS running within its electronic gene. In this fantasy world, StorageMojo enumerated the benefits of ZFS on the MacLeopard.

No More Corrupted Data
ZFS will eliminate data corruption due to power failures, flaky RAM, poor grounding, failing hard drives, driver glitches, and phantom writes. With ZFS, all blocks are checksummed and the checksum is stored in a parent block. ZFS always knows if the block is correct and/or corrupt making the entire data store self-validating.

No More RAID Cards or Controllers
ZFS implements very fast RAID that fixes the performance knock-off against software RAID making all writes the fastest kind. Simply add drives to your system and you have a fast RAID system minus the cables and enclosures required by SCSI and SATA drives.

No More Volumes
Each time a disk is added to the Mac, another disk icon appears on the desktop. ZFS eliminates concept of volume. Whether you're adding a disk or several disks to the system, it automatically joins the storage pool for greater capacity and less management.

Easy Backups
ZFS has a feature called snapshot copy. It creates a copy of all data at whatever any point in time. A backup is made by copying the snapshot to a disk, tape or NAS box. Snapshots can be created on every write just in case.

ZFS on a MacLeopard would be a great thing! If we only had a MacGenie to grant our wish!