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Sun’s ZFS filesystem, which the company has referred to as “the last word in filesystems,” was widely expected to be adopted by Apple for use in Mac OS X. However, support never materialized, and the open source project to port the filesystem was unceremoniously shut down last Friday. The (un)stated reasons at heart seem to be licensing issues, though there are also technological reasons why Apple may want to create its own advanced filesystem.

The ZFS filesystem is perhaps one of the first truly “modern” filesystems based on the concept of “copy on write.” In the case of ZFS, this is done at the block level, so when any block on a disk is going to be modified, a fresh copy of all the data for that block is written to a new block on disk, and the older block can be retained for snapshot purposes. The filesystem is meant to address the needs of ever-growing storage, with features like data integrity, integrated device management, instant snapshots, and facilities to deal with increasing concurrency.