Many top-rated Oracle professionals feel that RAID 1 is preferrable to RAID 5. You can read more about this topic on BAARF. You can see that I am one of the members of BAARF.
Databases tend to be write-intensive. Your temp tablespace, the online redo logs and the control files (at a minimum) experience high write activity. The write penalties associated with RAID 3 and RAID 5 can slow down your database application performance. However, RAID 5 is great for read mostly databases since you can have multiple database spindles performing your read operations. However, RAID 0+1, which does mirroring and striping, will enjoy the benefits for reading that RAID 5 does and not have a write penalty. So I prefer to stick with RAID 1 or RAID 10 (another term for 0+1) for my Oracle databases.
This was first published in May 2006