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ZFS to play larger role in future versions of Mac OS X


Sun Microsystems' relatively new ZFS filesystem will see rudimentary support under the soon-to-be released Mac OS X Leopard, but will eventually play a much larger role in future versions of the Apple operating system, AppleInsider has been told.

People familiar with the matter reveal that Apple on Wednesday provided developers with "ZFS on Mac OS X Preview 1.1" and associated documentation, in which the company asserted that it alone was responsible for porting the filesystem to Mac OS X.

The Cupertino-based firm also officially confirmed to developers receiving the pre-release software that Mac OS X 10.5 Leopard — due out later this month — will officially support ZFS, albeit restricted to a read-only implementation with which no ZFS pools or filesystems can be modified.

Developers receiving the latest ZFS preview, however, are granted access to full read and write capabilities under Leopard, including the ability to create and destruct ZFS pools and filesystems.

The developer release, those people familiar with the matter say, is a telltale sign that Apple plans further adoption of ZFS under Mac OS X as the operating system matures. It's further believed that ZFS is a candidate to eventually succeed HFS+ as the default file system for Mac OS X — an unfulfilled claim already made in regard to Leopard by Sun's chief executive Jonathan Schwartz back in June.

Unlike Apple's progression from HFS to HFS+, ZFS is not an incremental improvement to existing technology, but rather a fundamentally new approach to data management. It aims to provide simple administration, transactional semantics, end-to-end data integrity, and immense scalability.

According to Sun's description of ZFS, the filesystem offers a pooled storage model that completely eliminates the concept of volumes and the associated problems of partitions, provisioning, wasted bandwidth and stranded storage. Thousands of filesystems can draw from a common storage pool, each one consuming only as much space as it actually needs. Therefore, Sun says, the combined I/O bandwidth of all devices in the pool is available to all filesystems at all times.

In addition, ZFS provides a feature called "disk scrubbing," which is similar to ECC memory scrubbing; it reads all data to detect latent errors in the file system while they're still correctable.

"A scrub traverses the entire storage pool to read every copy of every block, validate it against its 256-bit checksum, and repair it if necessary," the description reads. "All this happens while the storage pool is live and in use."

A more comprehensive description of ZFS, along with several other features it offers, is available on Sun's OpenSolaris website.