File Fragmentation and File System Resiliency

Eric^2 asks: "We have an old NT server that we are going to replace sometime this year. It has Diskeeper on it to do disk defragmentation. I remember from DOS that this was also a BIG problem, and am curious how the EXT2FS handles file fragmentation. Whatever we put in to replace that NT box needs to be fairly resiliant, and I was thinking either FreeBSD, or maybe Linux with the XFS file system, as it's supposed to be more fault tolerant. I would appreciate any suggestions that you may have! Is there a more robust solution than XFS for Linux? FreeBSD? Should I stick with NT and Diskeeper? "