Consider the following quotes from Apple’s description of Time Machine:
… what makes Time Machine different from other backup applications is that it not only keeps a spare copy of every file, it remembers how your system looked on any given day — so you can revisit your Mac as it appeared in the past.
The first time you attach an external drive to your Mac, Time Machine asks if you’d like to use that drive as your backup. Say yes and Time Machine takes care of everything else. Automatically. In the background. You’ll never have to worry about backing up again.”
To me that sounds a lot like Time Machine is using ZFS Snapshots.
Snapshots are copies of the entire file system, they are not the same as backups; they are much more efficiency and they are faster. This is because a snapshot only stores the individual disk blocks that have changed, so it uses far less disk space than a traditional backup. Snapshots also happen instantaneously regardless of the size of the file system size, indeed the time it takes to create a snapshot is often so small that there appears to be no delay. In other words backups happen automatically. In the background. And the entire system is backed-up.
It seems that ZFS will not be the default system in Leopard (bugger), instead:
ZFS “is only available a read-only option from the command line,” according to an Apple spokesperson.
In a follow-up interview today, Croll explained, “ZFS is not the default file system for Leopard. We are exploring it as a file system option for high-end storage systems with really large storage. As a result, we have included ZFS — a read-only copy of ZFS — in Leopard.”
“Read-only means that at a later date, if there are ZFS volumes, those systems would be able to read ZFS volumes,” Croll added. “You cannot write data into the system. It will allow you to read ZFS volumes later.”