Test 2: Streaming Reads

We made a statement in the initial article that turned out to be wrong. We said that hard drives would consume close to idle power for sequential read operations. This is true for many 3.5” hard drives, where mechanical activity requires more power than in 2.5” notebook drives. Unfortunately, we did not take the time to repeat that analysis with 2.5” drives. In fact, notebook drives oftentimes reach peak power when they have to provide high bandwidth data streams.

Let’s look at the benchmark results for our streaming read IOMeter pattern, which applies 100% sequential reads at 64-KB, 128-KB and 256-KB block size in an equal proportion.

All of the Flash SSDs with the exception of SanDisks’s slower, but more efficient, SSD5000 outperform the mechanical hard drives when it comes to delivering throughput. More I/Os per second translate into more blocks of 64, 128 or 256 KB information per second, which again translate into higher data transfer rate. The results are very different for writes, but since read activity typically dominates over writes in desktop environments, we do not dig into it at this time. The Samsung HDD, which is one of the best performers when it comes to throughput, shows the best result for the mechanical hard drives. And again, OCZ is the one to beat everyone else in performance. Time to look at the power consumption for streaming reads:

Clearly, high bandwidth streams cause all the hard drives to reach their peak power, although many Flash SSDs utilize more power for sequential access. Only the new Seagate Momentus 5400.5 can beat the Crucial and Mtron Flash SSDs. The Super Talent MasterDrive does well, but the real winner is the new OCZ Flash SSD again. It only requires 0.6 W at maximum sequential throughput, and it delivers the highest bandwidth by doing so. Remember that the SanDisk performance is disappointing, which reflects on the performance per watt results.

As expected by many of our readers, a Flash SSD provides better performance per watt when operating at maximum sequential throughput. However, the only drive that actually showed mind-blowing results is the OCZ SATA II 2.5” SSD, which we did not have when we compared SSDs for our initial article.