Sun's ZFS file system has been rumored to be included in Leopard for quite some time now. Today Sun gave indication that ZFS will be a part of OS X 10.5. Ok, so what? That news in itself isn't very informative. Several months ago the Machine Check Exception Blog had a great post on why ZFS will matter to: Laptop / Desktop users, to Workstation Users, to Server Admins, and even why it won't matter. If you're curious about ZFS give this a read. I've put Why ZFS Will Matter to Laptop / Desktop Users below since that covers most of us.

Why ZFS Matters to Laptop/Desktop Users

People with iBooks, MacBooks, Powerbooks, Mac Minis, and iMacs all have generally the same storage setup: a single hard disk with capacity ranging from 40-500 GB. A lot of the magic of ZFS does not become manifest until you have several disks, but even with one, you can benefit in several ways:

Filesystems can be compressed. Unlike a compressed disk image, a compressed ZFS filesystem is read/write. Moreover, the compression flag can be turned on and off on the fly. New data will be compressed (or not) as per the flag, and old data will be left as is. Compressed filesystems are great for data that you don’t access very often, or data that compresses very well.

Filesystems are nested and making them is as easy as making a directory. This in itself is not very interesting for laptop/desktop users, but combined with compression, this means that you can effectively turn on compression for just a subfolder on your drive.

Every block of data on the disk is checksummed so errors can be detected during read operations. Many common hard drive failures are catastrophic, and painfully obvious when they happen. But it is possible for your data to be corrupted on disk in ways that you, and the hard disk, will never notice. While checksumming will not allow you to recover your data, it will let you know when you should go retrieve a file from your backup. (You are backing up, right? Go buy an external Firewire disk and SuperDuper!, and start doing it right now. It is easy, fast, and you’ll thank me later.)

Space-efficient and fast snapshots. A snapshot allows you to see your filesystem as it was some time in the past. ZFS is designed to snapshot a filesystem in constant time, no matter how much data you have, or how frequently you snapshot it. Moreover, the snapshot is very space efficient. Identical blocks are shared between snapshots and the live filesystem until they are written to. The space required for snapshots is therefore mostly a function of how quickly your files change, and not so much how often you make a snapshot. It’s like version control for your entire computer!

Apple’s much discussed Time Machine feature in OS X 10.5 is a great example of the interface possibilies when you have snapshots available. However, Time Machine does not appear to require ZFS, which means that Apple had to bolt snapshots onto HFS+, a complex and awkward task. Snapshots in ZFS are cheap and easy.