Very Cool. Why?
Here are the highlights of some of the changes you’d see with ZFS on Leopard, the next version of the Mac OS.

No More Disk Warrior
Data corruption on PCs and Macs is a sad and stupid fact of life. Power failures, flaky RAM, poor grounding, (slowly) failing hard drives, driver glitches, phantom writes and more conspire to rot your data.

ZFS eliminates that. All blocks are checksummed and the checksum is stored in a parent block. ZFS always knows if the block is correct and/or corrupt. Every block has a parent block (with one obvious exception that gets special treatment), so the entire data store is self-validating. You’ll never have to wonder if all your data is correct again. It is.

No RAID Cards or Controllers
ZFS implements very fast RAID that fixes the performance knock-off against software RAID. In ZFS all writes are the fastest kind: full stripe writes. And the RAID is running on the fastest processor in your system (your Mac), rather than some 3-5 year old microcontroller.

Just add drives to your system and you have a fast RAID system. With Serial Attach SCSI and SATA drives you’ll pay for the drives (cheap and getting cheaper), cables and enclosures.

No More Volumes
Every time you add a disk to your Mac you see another disk icon on the desktop. If you want to RAID some disks you use Disk Utility (or something) to create the volume. Slow, error-prone, confusing.

ZFS eliminates the whole volume concept. Add a disk or five to your system and it joins your storage pool. More capacity. Not more management.

Backup Made Easy
ZFS does something called snapshot copy, which creates a copy of all your data at whatever point in time you want. Copy the snapshot up to a disk, tape or NAS box and you are backed up.

Create a snapshot on every write if you want, so if your database barfs you can go back to just before it choked.

But That’s Not All!
For in-depth treatment of ZFS see here and here. Includes links to more technical info and benchmarks.