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?
ADDED INFO
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!
Best Answer
I think user71281 implies that your RAID controller (or driver) is messing up. When you go through the RAID setup of your controller (or driver), a RAID10 setup should never be slower then a simple RAID1.
Your RAID solution has either allowed you to setup an extremely inefficient RAID10 array, or you have uncovered a bug. Maybe performance improves with an 8th pair? Or maybe when you reduce the setup to 4 pairs? This last option may mean you have to upgrade to 146GB disks.
But I'd check for firmware updates first, and check how much RAM is on the RAID card. It didn't switch off its caching function because of a dead BBU (battery backup unit), did it?