Dell PERC 6/i RAID Performance Testing

We recently received a new Dell R710 with a PERC 6/i RAID controller and six 15k SAS drives. I have been doing some performance testing using hdparm and seeker on two different configurations and I'm not quite sure what to make of the results.

Configurations:

6 Disk RAID 10 - 64k stripe - Write through, no read ahead - RHEL 5.5

Results:

Timing buffered disk reads: 1024 MB in 3.01 seconds = 340.69 MB/sec

Results: 206 seeks/second, 4.848 ms random access time (137662331 < offsets < 436165962118)

4 Disk RAID 10, RAID 1 for OS - 64k stripe - Write through, no read ahead - RHEL 5.5

Timing buffered disk reads: 956 MB in 3.01 seconds = 318.13 MB/sec

Results: 209 seeks/second, 4.771 ms random access time (58179688 < offsets < 292314580383)

My first question is whether these results are within the expected range for our hardware. Using a RAID calculator it seems that I should be able to get higher speeds out of either configuration.

Also, while the first configuration performs slightly better, the second configuration would allow us to separate our MySQL databases from and isolate other IO to the RAID 1. I feel like that isolation would prove more beneficial than a few more MB/s.

Thoughts? Any input is appreciated.

Answer

Yeah. You TOTALLY focus on the wront number. Nothing cares about MB/s on a server. The ONLY relevant item is IOPS. Because moves destroy IO.

Make a check that checks random IO of appropriate size for your database server. Because most of the time you will have various processes hit the discs with different requests, so it is purely random.

So, what IOPS numbers di you have?