One of my clients is in the process of standardizing all their servers on RAID 10. We discovered one of their smaller servers had been delivered with RAID 5 already configured. I took the opportunity to run some tests on the drives prior to reconfiguring them into RAID 10. My tests weren't very scientific. I just used SQLIO.EXE to generate random 8KB reads and writes.
Reads were just a little bit better but writes were almost twice as fast. This makes sense as the array isn't spending time computing the parity information. Some notes on my setup:
- There are FOUR drives in the array.
- Each drive was a 146GB 15K SAS drive with 8MB of cache.
- The test was performed with a 5GB file. I'd prefer a larger file but my time was limited and the RAID 5 tests were already completed.
- The controller was one of the low-end PERC controllers from Dell.
- 64KB random writes showed a similar doubling of IOPS. I didn't test sequential writes.