Waiting too long to upgradeI had related at "Another Raid Failure" that an initial attempt to rebuild the raid had failed, and left the story with fresh drives on order and winging their way toward us. The drives did arrive, but unfortunately the rebuild still failed. A Knowledge Base article suggested that there might be unreported problems on other elements of the array, with the suggested solution of blowing it all away and recreating from scratch. As we still had some suspicions about backups at that point, I didn't want to do that until we had unquestioned good recovery capability.
Degragmentation wars The subject of disk fragmentation will almost always draw heated arguments but seldom gets treated in its entirety. I'm going to try to do that here, but will probably miss a point or two: this is an extraordinarily complex subject and honestly there aren't any easy answers.
sparse files -->Re Problems withbackups/restoresWow, that's the worst explanation of sparse files I've ever seen. Sparse files were actually a space saving "trick" introduced in Unix filesystems a long, long time ago. The need sprang from hashed files, which is probably where "index" got into your muddled explanation.