Every filesystem gets fragmented. Filesystems simply cannot guarantee that file allocation and growth is continuous on a hard drive. It's just impossible (unless you're ready to sacrifice a lot of performance doing "on the fly defragmentation" or a lot of space to pre-allocate a lot of extra blocks to accomodate the growing and changing of files.) The performance of Windows' NTFS filesystem and other Unix filesystem under fragmentation loads is very similar and all much better than FAT based filesystems were. That's the point, the "slow down" isn't quite as there on NTFS, and it is about the same you would suffer from HFS+. If you read the early Microsoft docs on NTFS, this was one of its selling point. Now that they bothered to produce a defrag tool, why wouldn't they promote it and its use ? Again, I won't fight this holy war about file fragmentation on disks. It's a lost cause. People swear by defragmentation to keep a filesystem's performance up, I know that's grasping at straws and the benefits are negligible enough that I shouldn't bother with it.