We have a bunch of Dell PowerEdge 2950 servers as virtual machines servers for our development environments. On our latest server someone made a mistake and ordered a 2 RAID1 topology, not our typical 4 to 6 RAID5 topology.
We ordered 2 extra disks and reinstalled the server. Here's how it benchmarked as 2 disks on RAID1:
Here's how it benchmarks now as 4 disks on RAID5:
As expected we got a great improvement with little investment, still having a fault tolerant scenario compatible with our development server deeds. A higher sustain rate sequential read speed. If we had 6 disks, I'd expect still a better performance.
NOTE: we didn't actually add 2 disks, we replace 2 x 300GB disks with 4 x 400GB ones.