Sun's high-performance ZFS file system has been hinted to be coming to Mac OS X Leopard for some time now. Even Sun's CEO said at one point that ZFS was on, but Apple quickly shot down that claim. Then ZFS was said to be available as a read-only option. Now a new episode in this ZFS soap opera reveals that the revolutionary file system could very well be coming for Leopard, even if it doesn't ship in time for the OS launch this month.
Apple has now issued "ZFS Read/Write Developer Preview 1.1 for Leopard," an update to a previous build from June that enables full read, write, creation, and destruction abilities of ZFS file systems for developers testing Leopard. Before you get your hopes too high though, Apple confirms in the release notes of this developer preview that only read access will be shipping with 10.5.0. It gives no ETA for when full read/write features will be be available, nor a confirmation that full ZFS capabilities are coming specifically to Leopard.
That said, this offering—at worst—is a good sign that Apple has committed to bringing ZFS to Mac OS X. Whether a 10.5.x Software Update will bring ZFS support (possibly as an optional download?) remains to be seen.
