Comparisons And Synthetic Benchmarks
We rarely use the performance SATA charts, and the latest test pool is quite a bit different than the last time we covered a new SATA SSD. Crucial replaced the MX200 with the new 3D-enabled MX300 and Corsair's Neutron XTI now represents the best of the Phison S10 products. The XTi is the first SSD to feature Phison's Double DDR technology, which uses twice as much DRAM for the Flash Translation Layer (FTL).
Three products carry over from the previous test selection. The Samsung 850 EVO represents the best of the mainstream market. At one point, the EVO was just a few dollars more than low-cost entry-level products, but the price has crept up over the last few months while TLC-enabled products like the OCZ Trion 150 have dropped. The large gap makes the EVO a true mainstream, mid-tier product. The Samsung 850 Pro and SanDisk Extreme Pro represent the best performance that SATA has to offer. Both drives ship with a 10-year warranty and deliver exceptional performance during moderate and heavy workloads. The Toshiba VX500 aims to challenge these products while undercutting both on price.
We have three of the four Toshiba OCZ VX500 products and compare them to 512GB-class SSDs. The heavy black bar in the chart identifies the VX500 512GB. The VX500 256GB and 1TB are also in the test pool, but we will focus our commentary on the 512GB model.
Sequential Read Performance
The sequential read performance test reveals that the products fall into distinct performance bands at QD2. The only product with a serious disadvantage is the Crucial MX300, which Micron outfitted with its new 384Gbit 3D TLC flash. Crucial still positions the MX300 series for the mainstream market, but the hefty die density results in decreased performance at smaller capacities. The 3D flash comes alive in large capacities over 1TB, though.
The VX500 fares better than the MX300, but it still trails the other products. The two market leaders deliver roughly 20 MB/s more performance at QD2 than the competitors. The difference looks significant on paper, but under real-world conditions, the extra performance equates to a rounding error in the amount of time it takes to transfer a medium-sized file.
Sequential Write Performance
The sequential write charts also reveal different performance bands, and the humble Neutron XTI takes the podium while the Samsung Pro and EVO models trail close behind. The three VX500 drives reach 500 MB/s at QD2. We expected a little more separation between these three drives, but they all perform about the same with sequential data.
Random Read Performance
All three VX500 SSDs deliver abysmal random read performance. When I compiled the charts, I started to doubt if it was appropriate to compare the VX500 to the high-performance models. Later in the review, we will see a total 180-degree change during real-world applications. Toshiba's programming always gives us odd results in synthetic workloads, and it's been a long time since we've tested a Toshiba SATA SSD with a DRAM buffer. We've pinned the low random performance on the bufferless configuration used with the previous products, but there is more to the story.
The VX500 has a small DRAM or SRAM buffer to cache the LBA map, but the cache is not large enough to hold the map in its entirety. Toshiba likely uses algorithms to detect "hot" data on the drive, and then only caches the frequently accessed portions of the map. This technique allows the SSD to provide fast performance with frequently accessed and localized data, which is very common with applications, but performance suffers when requesting "cold" data (which can happen during synthetic benchmarks).
Random Write Performance
OCZ's VX500 specifications already tipped us off to expect low random write performance, but we didn't expect the low peak performance to drag down the low-QD performance, too. Toshiba will have a few hurdles to overcome with firmware tuning. Toshiba designed many of its SSDs for the OEM market where the biggest selling point is capacity and pricing. Retail products, especially anything from OCZ, come with additional performance scrutiny. Toshiba will need to listen to the team it acquired to gain insight into designing and selling high-performance products for the upgrade market.
80 Percent Sequential Mixed Workload
As mentioned, Toshiba client SSDs are much better than what the synthetic tests lead us to believe. The VX500 tackles sequential mixed workloads with ease and outperforms the competition. The results tell us that Toshiba isn't tuning for synthetic tests and is focusing on application performance instead, which is where optimizations really matter.
80 Percent Random Mixed Workload
The VX500 would lead another mixed workload test, but this time with random data, if we removed the two high-cost Pro SSDs. We would like to see the VX500 take it to the next level and compete with the two Pro products, but the low random read performance makes it a difficult task. A product can only start out with so much of a disadvantage before it gets to a point where catching up is impossible.
The three VX500 SSDs share nearly identical performance specifications, but larger capacity drives from the same family will almost always deliver higher performance. The bigger drives use larger DRAM buffers and more NAND, and that helps speed up performance. The VX500 512GB performs well compared to the other products in the chart. It doesn't outperform all of the drives in the sequential steady state tests, but it makes its mark in the middle of the field.
Performance consistency is what makes the SanDisk Extreme Pro stand out from the crowd. The drive also has high peak performance when we push it hard. The OCZ VX500 series has less consistency and a wider gap between its highest and lowest performance during the test. When you contrast the two we see what we are looking for, and also what we don't want to see. The VX500 has the widest performance variation of the drives tested, but it still performs much better than any of the TLC-based products (other than the 850 EVO). The VX500 series deserves comparison to the best SATA SSDs on the market, but it doesn't always come out on top of this group of powerful SSDs.