It happens rarely, but it happened to me already. Imagine you saved a file and backed it up. At some point (which is basically a question of time) your file get

It happens rarely, but it happened to me already. Imagine you saved a file and backed it up. At some point (which is basically a question of time) your file gets corrupted. You don't notice it since you don't touch that file very often. After a year or so, you try to open it and it fails. Then you go to your backup only to notice that the corrupted file has been overwriting your original file and the deletion of older backups resulted in your original file being long gone. Maybe you have a second backup? Have you ever had the opportunity to see a "slightly" broken hard drive continuously changing all your stuff by just a little bit? Somebody's to blame, right? Well, yeah, basically it's the file system's highest priority not to break your data. And, of course, to tell you when your data broke. HFS+ is just not capable of doing that. Then there's such things as RAID mirroring which really only makes sense if you know which blocks are the correct ones and which are the broken ones. The second major thing I'd really like to have are Snapshots. There's not much to be said here except that I'd really like to easily create a snapshot of the state of a disk. Roll back easily, setup your new computer without hassle. Time Machine Backups kind of tries to do that, but it's (in my opinion) a real pain, although it does some things that are useful. What Time Machine tries to do, is essentially to emulate a feature that should really be part of the file system. There's been a lot of progress on file systems but HFS+ is kind of stuck. HFS+ is basically an age-old thing that doesn't really have any more capabilities than back in the glorious Mac OS 8 days (Journaling was added sometime later), except that ever more stuff is put on top of it instead of improving the file system itself. Also, I really dislike the default being case-insensitive and case-preserving (apparently things break if you make it case-sensitive) but maybe that's just me. If you ever get the chance, try reading up on ZFS (or give it a try with, say, FreeBSD on a server). ZFS basically shows the capability of a modern file system.