Following up on the information iMore received yesterday on potential ZFS hooks in iOS 5.1, a reliable source let us know that Apple has been investing heavily in ZFS appliances from Oracle. (Whether or not this will be made public is unknown; it doesn't seem to be right now.)
Also, several of our readers familiar with ZFS wrote in to speculate as to why Apple may be exploring ZFS for use on iPhone and iPad. Broadly, it may have something to do with ZFS' snapshot technology. ZFS snapshots can be easily compressed and encrypted, de-duplicated, and can transfer delta (bit differential) updates between cloud and device. The snapshots can also work like Time Machine, easily and efficiently providing incremental backup and restore capability from an hour ago, a day ago, a week ago, or more, asynchronously and block by block. Here's what Wikipedia says about ZFS snapshots:
An advantage of copy-on-write is that when ZFS writes new data, the blocks containing the old data can be retained, allowing a snapshot version of the file system to be maintained. ZFS snapshots are created very quickly, since all the data composing the snapshot is already stored; they are also space efficient, since any unchanged data is shared among the file system and its snapshots.
Writeable snapshots ("clones") can also be created, resulting in two independent file systems that share a set of blocks. As changes are made to any of the clone file systems, new data blocks are created to reflect those changes, but any unchanged blocks continue to be shared, no matter how many clones exist. This is an implementation of the Copy-on-write principle.
Snapshots is only one of the features of ZFS (Zettabyte Files System), the advanced file system created by Sun, now owned by Oracle. Apple included a partial port of ZFS in earlier versions of Mac OS X but pulled it before the official release. It's a file system particularly well suited for cloud environments and storage pools, which might be why Apple is looking at it again in the post iCloud.
Apple is an incredibly private company that works hard behind the scenes in order to present a beautifully packaged, highly polished product to consumers. No doubt there is a lot of really cool, really geeky technology at the core of iCloud, for example, but all most of us see are elegant interface elements in Settings.app that, when tapped, all but transparently backup and restore our iPhones or iPads.
If indeed Apple is planning on using ZFS to make iCloud backups and restores better, it will probably be invisible to end users. One day, iCloud will simply work better, faster, and even more reliably.