According to some blog-posts and insider news, ZEVO will bring ZFS to OS X.

ZFS [1] (aka Zettabyte File System) is an ultra-stable and reliable file-system format mostly used for servers. Up to now it was and is supported by Solaris and FreeBSD. ZFS-formatted drives were mounted in 10.6 Snow Leopard as read-only, but the support was completely canceled in 10.7 Lion.

One of the clues in ZFS is that while editing e.g. a document, the original file will be untouched until the changes will be stored completely. Until that point all temporary changes are done with shadow-copies of the original file.

Zevo will be available [2] in three versions, Silver ($19,95) and Gold ($39,95) with a Time-Machine like backup-tool and Platin, which will be released in this spiring.
The differences are that the Silver Edition supports one drive, only, formatted in ZFS-file format. The Platin edition, which is not released yet, will have some extra features which are not “included” in the ZFS implementations of FreeBSD or Solaris.