RAID Scaling Charts, Part 1

Test Setup

All tests were performed at controller defaults.

Experiences

All tests were run with two to eight Samsung HD321KJ, but using only 80% of the capacity; we did not use the full capacity of 320 GB per drive, in order to keep the test runs short. This reduced the test run times and made sure that the drives operated at maximum performance, because they never reached the inner sectors of the rotating media, which deliver the lowest transfer rates.

It took four to six hours to complete one benchmark session for one RAID configuration, including throughput, access time and I/O benchmark runs. Initialization was required for all RAID arrays except the RAID 0 setups; this took an additional 20 minutes.

We also made a nice discovery with regard to drive power supply: we first attached multiple drives to a single power rail of the power supply used. This seemed to work well, as the spinup typically draws enough power to cause trouble and we didn’t encounter problems. However, single drives dropped out of the RAID array during the benchmarks once in a while. We blamed the drive when it first happened, and pointed at the RAID controller after experiencing the problem a second time. Then we split the power supply to three different rails and voilá - the problems disappeared.