I've always been wondering about filesystems which pretend to be immune to fragmentation - sounds like hairy algorithms at work.

And disk tool vendors will FUDdily try to convince you that defragmentation cannot do any harm anyway, so why not do it?

The detailed analysis done by Amit Singh shows that fragmentation is indeed well tamed by the macosx hfs+ filesystem.

Amit says that defragmentation shouldn't be necessary as the system does a very good job of preventing it. Good news!

Note that (shame on me ;-) I've only read the conclusion, but the post looks serious. I have saved it in my toRead folder for one of these rainy days...