Re: Fragments or RAID 5?

>Anybody out there knows which provides the best performance: fragmenting >tables (round robin) on multiple hard drives or letting a RAID5 controller >do the work? > > In general I do not like to see RAID5 environments for several reasons, but chiefly because a lot of customers that have used RAID5 develope a false sense of security and have stopped taking backups. This works OK until there is a double disk crash. Also, with RAID5, multiple disk actuators are required to do a single physical IO and this results in writes being a tad slower because more seeks are required on the platter. I'd rather see RAID2 or RAID1. Round robin fragmentation will not buy you very much unless 1) you are currently doing a lot of scans of the entire tablespace (parallel scans), or 2) there is a "lot" of contention and you are doing a lot of writes, or 3) you want to be able to recover pieces of the tablespace instead of the entire table. If you can fragment by expression, then you will be able to take advantage of fragment elimination. I guess that I really don't see why RAID5 would be associated with fragmentation at all. They really don't have anything in common and can co-exist. Madison Pruet