HD Tune — Transfer rates
HD Tune lets us present transfer rates in a couple of different ways. Using the benchmark's "full test" setting gives us a good look at performance across the entire drive rather than extrapolating based on a handful of sample points. The data created by the full test also gives us fodder for line graphs.
To make the graphs easier to interpret, we've greyed out the mechanical drive. The SSD results have been colored by drive maker, with the RevoDrive set apart from OCZ's other offering in a yellow shade halfway between mustard and gold.
Weird. Although the RevoDrive has a higher average read speed than the other SSDs, its transfer rate bounces between high and low extremes with alarming frequency. Even the Revo's maximum read speeds are substantially slower than the drive's projected peaks.
The RevoDrive's transfer rate profile looks even stranger in HD Tune's write test. There are actually two oscillation patterns here. The series of regular spikes mostly matches the behavior we've observed from other SandForce-based SSDs. However, the spikes also follow a secondary wave that we haven't seen before.
Average out all those peaks and valleys, and the RevoDrive 3 X2 scores lower than the Samsung 830 Series SSD by a wide margin. The drive's average write speed barely breaks 300MB/s, which is a far cry from the drive's published speed ratings.
These first tests were run with HD Tune's default 64KB block size, which is obviously less than ideal for the RevoDrive. Out of curiosity, I fired up the same tests with an 8MB block size, the largest one available. The RevoDrive got a lot faster, so I ran the same tests on the Intel 520 Series and Samsung 830 Series for comparison.
The larger block size works out exceptionally well for the RevoDrive 3 X2, whose read speed averages nearly 1400MB/s. Perhaps more importantly, there's none of the wild variance we saw in the previous tests. The other SSDs also post higher sustained read speeds than they did with the 64KB block size, but their gains are in the 16-28% range. The RevoDrive's read speed improves by a massive 170%.
Switching to the 8MB block size also improves the RevoDrive's write rate. The drive still exhibits a lot of oscillations in this test, but the secondary wave is gone and the average speed has tripled versus the 64KB block size. While the other SSDs enjoy performance gains, too, the improvements amount to less than 10%.
We asked OCZ if the RevoDrive is optimized for a particular block size and were told that 128KB should be "pretty close to best performance." Not in HD Tune. The Revo only manages an average read speed of 716MB/s with the 128KB block size. Oddly, the benchmark spits out an error when trying to perform its write test with the same block size.
HD Tune's burst speed tests are meant to isolate a drive's cache memory. There's no option to change the block size here.
The RevoDrive 3 X2's read and write burst speeds are notably slower than most of the other SSDs, including those based on the very same SandForce controller—albeit only one of them.