RAID 10 vs. RAID 5 Performance

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.
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