We have a new Dell 2950 with PERC 6/e and 14 external SAS 15K 73GB drives. An Oracle 11g database job takes 3 hours to run with the drives set as hardware RAID 10 (striped across 7 mirrored pairs). The database size is about 26GB. The same job running on just two drives in RAID 1 takes only 1 hour. OS is Win 2008 R2.
Before we change the RAID level (with considerable downtime) on the production box, does anyone know why we're seeing this odd result, and if there's a better way to fix it?
PERC 6/e should be running the latest firmware and cache battery OK.
FINALLY, THE REAL STORY
After speaking w/the DBA, my face is red. Turns out the RAID 1 is seven RAID 1 volumes of two drives each. The data tables and indices were assigned to each volume to minimize contention. Apparently a good DBA can get more performance from 14 drives than a RAID 10 controller striping blindly across them without regard for file access patterns. Some SANs claim to intelligently migrate files to improve performance, but if there's a bake-off anytime soon, my money's on our DBA!