While I am happy that Apple have at last committed to replacing HFS+, I'm wondering why they didn't use ZFS rather than reinventing the wheel. It's not like it's a particularly easy wheel to reinvent either; the amount of effort which goes into a filesystem like ZFS is non-trivial. Why not build on top of that?

I would have greatly appreciated being able to use ZFS with MacOS X, for datasets, snapshots, sending them to remote pools for backup etc. It would have made it directly interoperable with a lot of pre-existing and cross-platform infrastructure. (I couldn't care less if it didn't scale down to the "watch". Filesystems are not a one-size-fits-all affair.) I find it great that I can take a set of disks from e.g. Linux, run "zpool export", pull them out, and then shovel them into a FreeBSD system, run "zpool import" and have the pool and datasets reassembled and automatically mounted. Perfectly transparent interoperability and portability. While Apple like to do their own thing, this is one place I would have definitely appreciated some down to earth pragmatism and re-use of existing battle-tested and widely used technology.