We benchmark with HD Tune Pro over the full span of the drive using a 64 KiB write access pattern. What we're looking for is consistent write performance.
The test involves writing data to every sector of the drive while measuring speed and latency. In the graphs below, the orange line represents write performance and the yellow dots indicate the write access time.
Plextor M5 Pro
OCZ Vertex 4
Up until now, our benchmarks have left plenty of free space on each drive. It's only when we use HD Tune to write across the full span of our contenders that we see OCZ's Vertex 4 stumble as it switches from SLC to MLC mode (for an explanation of this, check out this page).
Although the 256 GB Vertex 4 is better able to mitigate the impact of the switch-over than the 128 GB model, there is still a performance degradation as free capacity is consumed. The phenomenal write performance we saw when the Vertex 4 was in SLC mode has to be tempered by the amount of space available and the size of the writes within that free space.
Our M5 Pro doesn't dominate, but its performance is both solid and consistent. However, it allows Samsung's 830 to emerge as the fastest drive in maximum, average, and minimum write speeds.
Next, we measured read performance, filling each drive using an Iometer test file before running HD Tune. We then used a 4 MiB sequential read access pattern across the full span of each contender.
Plextor M5 Pro
OCZ Vertex 4
Plextor's M5S does best in average read speed measurements, while Samsung's 830 and the M5 Pro finish neck and neck.
The Vertex 4 can't compete with the M5 Pro. Its read speeds start off a lot slower than the other drives, and then drop further as the benchmark gets to the last quarter of its run.
As far as large block read transfers go, there really isn't a whole lot of variation between the drives, so user experience in that context isn't going to change much from one model to the next.
Now, let's compare our Anvil's Storage Utility and HD Tune results to each manufacturer's sequential read specifications.
|Manufacturer Specification (MB/s)||ASU (MB/s)||HD Tune (Avg MB/s)||HD Tune (Max MB/s)|
|Plextor M5 Pro||540||504||496||504|
There is no universally accepted methodology SSD vendors use to rate their products. Most specs prefaced with an "up to," and a number of different metrics can be used to generate that value.
Our ASU and HD Tune results illustrate this nicely. The most notable deviation from manufacturer specs comes from OCZ's Vertex 4. The company states that is uses ATTO to come up with its sequential read speed numbers. We ran ATTO ourselves and, sure enough, on an empty drive using a 256 MiB test file and a 1 MiB access pattern, we achieved 560 MiB/s. But, if we increased the test file size, we were unable to replicate that number.
On the other hand, while Plextor's M5S slightly exceeds its specification in HD Tune, the M5 Pro missed its mark by 36 MiB/s.