Apple's Snow Leopard padded across the Mac World for the first time in public this week, accompanied by its silent twin, Snow Leopard Server - leaving little trace of ZFS.
ZFS is Sun's 128-bit Zettabyte File System with advanced data protection and storage virtualisation features. Sun had said Apple would adopt it.
The current Mac OS X version, 10.5 or Leopard, does have some ZFS support: witness this XServe software features listing. The same comprehensive software services list for Snow Leopard and Snow Leopard Server doesn't exist yet - not in public anyway - but the provisional information provided by Apple has zero mention of ZFS.
Snow Leopard is both smaller and faster than Leopard, releasing 6GB of disk space to Mac users. Removing a non-essential filesystem and allied services would have helped in the size reduction. We might suppose that ZFS is useful in instances of very large server storage configurations and most Mac servers aren't massive in storage terms, running quite satisfactorily on RAIDed drive arrays.
Mac desktops and notebooks don't need it at all, using generally one or two directly attached drives inside or outside the enclosure. Ergo Apple can dump ZFS as not being essential.
Snow Leopard Server's core technology features don't include any major changes to the file systems themselves, apart from those contingent on full 64-bit support and so forth. We're told HFS+, its extended file system, features 32-bit allocation blocks, file system journalling, software RAID with striping (RAID 0), mirroring (RAID 1) and mirrored striping (RAID 10), long filenames and international support, and case sensitivity.
Snow Leopard has been billed by Apple as a series of refinements of Leopard to make it smaller and faster, with its server version described as being "easier than ever for the people in your organization to collaborate, communicate, and share information... simple to deploy and manage". There's no significant addition of functionality here.
Snow Leopard adds incremental improvements to Mac OS X and ZFS didn't make the cut. Perhaps the next major release of Mac OS X - Mac OS X1 maybe - will be the one to have full ZFS support. ®