I'm trying to settle an argument between myself and a friend - My friend seems to think that optimizing and defragmenting a hard drive is a necessary maintenance task in OS X. After a recent bout with Norton Speed Disk, Disk Doctor and DiskWarrior he's rendered several previously bootable disks unmountable on several occassions - but is still convinced that there's bad sectors out there that need to be cleaned up on the drives. He says "don't shoot the messenger" in regards to these tools - but I can't help but think those tools might have caused more problems than they supposedly identified and tried to fix. My thoughts are that the new UNIX underpinnings of OS X do a much better job of handling fragmentation and although I'm sure it still occurs at some level, it's not enough to seriously hamper performance. I also think that OS 9 and windoze OS's did a very poor job of handling files and that why those tools are so predominant on those platforms. I've played with Linux for a couple of years and have never heard of a defrag tool for any *NIX. What are the significant differences between HFS+ and UFS systems in regards to fragmentation? Does having a drive with OS 9 and OS X installations cause optimization/defrag nightmares? What roles does the fsck utility play? Isn't that executed as a disk check everytime OS X boots? Is a disk optimizing tool needed for OS X? Should it be part of a regular maintenance schedule? Is so, what is the best tool? Thanks in advance for your comments.