ZFS: ***?

Question

Ok, I confess that I instinctively hate anything new (except OS X itself, back when it was new).
This one, though, has me worried. I've never really quite bought the idea that HFS+ is somehow better than a normal unix file system, but mdfind and so forth at least finally convinced me that there was a point to the madness (however misguided).
So why yet another weirdo file system? Will this require us to reformat all our drives? Is there a chance that data backed up on HFS+-formatted drives and DVDs may one day be inaccessible?
I'm already quite worried, even though 90% of what I care about can live happily on any unix file system.
Darn censor won't let me type WTF.

Answer 1

Most file systems have failed to keep pace with the tremendous growth in storage needs (or at least availability) over recent years.
10 years ago hard drives were still being measured in megabytes. Now they're approaching terabytes - and that's just single drives. Once you head into RAID and arrays of drives you can even get into petabytes (thousands of terabytes), o even exabytes (thousands of petabytes).
It's hard to see how anyone could have foreseen that kind of growth, so it's not surprising that current generation file systems just aren't geared for it.
So, along come the latest filesystems including ZFS (although there are many others). They're designed around the cutting edge of storage needs today (and hopefully tomorrow).
Modern filesystems also implement better security protocols - something that wasn't as important a few years ago, and can leverage faster CPUs to offer things like on the fly encryption (to protect data) and checksumming (to ensure the integrity of the data).
Then comes things like journaling (added to HFS+ recently) which improves performance, auditing (recoding who changed what and when), and snapshots (multiple point-in-time copies of files so you can revert to a previous version).
Most of these newer features were never envisioned 10 years ago, and some of them are hard to back-port to existing file systems without breaking compatibility.
Do you need some of those features? No - at least not now, but knowing that they're there (or the OS silently taking advantage of them) is a good thing.
As for the otehr questions - will you need to reformat? Yes - at least to use ZFS, but there's nothing to say whether this is required or just available. You may be able to opt to keep your HFS+ disks as they are. I guess we'll know more as Leopard Day approaches.
Even if ZFS does become the standard that doesn't mean that everything else is instantly obsolete. Old filesystems can still be accessed by newer OSes if support is included. Does that mean your HFS+ backup drive will still work in 10 years time? who can say, but ZFS's snapshot feature alone probably means you want to switch your backups to ZFS as soon as possible.
As for DVDs I wouldn't worry about them. Their format is well defined and there are millions (billions?) of them already out there and, more importantly, not able to be changed due to the read-only nature of the disks. Any OS is going to need to support DVD-based formats for the foreseeable future.