Apple will announce this, he said, at Apples Worldwide Developers Conference June 11-15 in San Francisco.
Some Mac observers, including John Gruber of Daring Fireball have suggested that Schwartz misspoke, meaning instead to say that ZFS will be a file system option for Leopard.
Screen shots of Leopard betas that show the option to format a ZFS disk have been posted online for months.
However, Marc Hamilton, vice president for Solaris marketing at Sun, wrote on his blog that "Jonathan [Schwartz] noted that Apple will announce this week that the ZFS file system from OpenSolaris will become Apples new default file system."
ZFS could offer many potential benefits, such as "disk scrubbing" to prevent and correct latent errors on disks; a more efficient I/O engine; the ability to read and write to compressed file systems; and unlimited "snapshots" and "clones" that enable easy and quick backup and restores.
But implementing a new file system presents challenges. Mac OS Xs standard file system is currently "journaled" HFS+ (Hierarchical File System Plus), a descendent of HFS, which Apple debuted in 1985.
Currently, there is no migration path to ZFS for data-filled disks formatted in other file systems. Apple would have to present a simple, reliable conversion tool for users upgrading to Leopard from all previous versions of Mac OS X.
Still, Apple has a history of supporting more options than are commonly used.
The existing version of Mac OS X supports formatting disks in the UFS (Unix file system) format. However, Apple documents say that though using this disk as a startup volume "may be possible," it is not recommended.
Apple did not respond to requests for comment on June 6.