I will quote from the Oracle 9i bible(Performance Tuning Tips and Techniques)....p.65

"Raid 1+0 This level provides mirrored disks and striping. This incorporates the advantage of the first two RAID levels by providing the disk I/O benifit of RAID0 to the redundancy provided by RAID1.For high read/write environments such as OLAP,where sporadic access to data is the norm, this RAID level is recommended".

and

"RAID5 ...It is a low-cost solution that is inefficient for write-intensive applications."

--If you can get the book over the weekend read chapter 3.--