Results: PCMark 8 Storage Consistency Testing
Futuremark's PCMark 8 expanded storage tests are awesome. With so much data and a comprehensive testing regimen, we can really drill down on drive performance.
First, the raw block device (there is no partition) is preconditioned twice by filling the entire accessible LBA space with 128 KB sequential writes. Once that is completed, the first Degradation Phase randomly writes blocks between 4 KB and 1 MB in size to random LBA spaces on the drive. Since the writes aren't 4 KB-aligned much of the time, the SSD's performance drops quickly. After all, non-4 KB-aligned accesses create overhead and generally increase write amplification significantly.
The first Degradation Phase begins with 10 minutes of those punishing random offset writes, after which each PCMark 8 activity trace is played against the SSD being tested. The successive degradation rounds are similar, except an additional five minutes are tacked onto each iteration. After eight repetitions, that write period expands to 45 minutes.
Next comes the Steady Phase. Each of five Steady Phases writes 45 minutes worth of random offset data prior to trace playback, pushing the drive even harder and making it more difficult to perform housekeeping duties. With fewer blocks available for writing, latency increases substantially.
Lastly, PCMark 8 moves into a Recovery Phase, which consists of five idle minutes before trace playback. Repeat that five times, and the test concludes.
For more information on the test and how it works, check out a more in-depth description, check out the Plextor M6e 256 GB PCI Express SSD Review: M.2 For Your Desktop.
Storage Consistency With PCMark 8's Adobe Photoshop (Heavy) Trace
Because there are 18 individual rounds packed with 10 traces each, we need to focus. We'll choose one trace, Adobe Photoshop (Heavy), and keep tabs on it through the entire extended run.
A few pages ago, I mentioned that the lack of additional over-provisioning on Transcend's SSD340 was going to hurt it. Well, this is where we see the pain first. The JMicron-powered drive just doesn't get much of a bandwidth boost in the later Recovery phases. In fact, it's only slightly faster than it was in the Degrade phases.
Of course, that's disappointing, though, given what we saw on page five, the numbers make sense. At least the SSD340 beats the more expensive Plextor M6M.
In this test, we're taking that same Adobe Photoshop (Heavy) trace and using average read and write latency to illustrate responsiveness. We'll sprinkle in some competing drives for comparison, too.
The Tom's Hardware Storage Bench trace test on the previous page made it clear that Transcend's SSD340 encounters higher read service times than competing solutions. We see the same behavior yet again.
Write latency falls in line with some of the other drives we're using for comparison. That L85A flash doesn't do JMicron's JMF667H any favors.