One bit of news about Mac OS X 10.5 (Leopard) we can expect to hear during the World Wide Developer Conference is that Apple will be replacing the HFS+ file system with Sunis ZFS file system. Sun CEO Jonathan Schwartz revealed the news during a presentation in Washington D.C. on Wednesday, according to CNET News.

ZFS, or Zetabyte File System, is Sunis open source 128-bit file storage system that was originally developed for the Solaris Operating System. One of the advantages of ZFS is that it is not constrained by the file size and maximum number of file limitations found in most operating systems including Mac OS X 10.4. Instead, it is capable of storing substantially greater numbers of files - to the tune of billions more.

ZFS also has the ability to use hard disk space more efficiently with variable size data blocks, dynamically stripe data across multiple drives, and take "snapshots" of an operating system and data so users can roll back to previous versions.

Apple has not officially announced that it will be adopting the ZFS file system with Mac OS X 10.5, but based on Mr. Schwartzis comments it seems very likely that CEO Steve Jobs will discuss it during his WWDC keynote address on Monday.