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Benchmarks And Comparisons
Comparison Products
We built a diverse group of low-cost SSDs to compare with the product under review. Our samples follow the latest market trends; all but one SSD utilizes three-bit per cell (TLC) flash.
The Samsung 850 EVO 1TB is the gold standard for entry-level to mainstream products. The SSD has been on the market for more than two years and it features the best software package on the market. Samsung's Magician software includes Rapid Mode, which is a system memory cache that buffers random data writes and flushes the data sequentially to the drive. The caching reduces flash wear and increases performance. It also features TurboWrite, which is an SLC-programmed buffer. The 850 EVO ships with a 5-year warranty. The 850 Evo's pricing often varies month-to-month, and it has steadily increased since the release of the 750 EVO series with planar TLC flash.
The Corsair Force LE, MyDigitalSSD BP5e and OCZ Trion 150 all use an 8-channel, feature rich controller co-developed by Phison and Toshiba. Corsair and OCZ offer average software packages, but both lack a system-level memory cache algorithm. Firmware updates on some products with this controller enable a new program mode that bypasses the SLC cache when the buffer is full. Direct-to-die writes nearly double sustained sequential write performance when the SSD operates outside of the SLC buffer, which is much better than previous program modes. These products include a 3-year warranty.
The Crucial BX200 and Mushkin Reactor both feature Silicon Motion controllers. The BX200 features Micron's 16nm TLC flash with an SLC program mode. The Reactor utilizes Micron's 16nm 128Gb MLC flash without an SLC programming mode. Crucial offers its Storage Executive SSD software package that features Momentum Cache, a DRAM cache function. These products carry a 3-year warranty.
Sequential Read Performance
To read about our storage tests in-depth, please check out How We Test HDDs And SSDs. Four-corner testing is covered on page six of our How We Test guide.
The Reactor is the only MLC-enabled SSD in the group of low-cost 1TB products, and it tailed the TLC drives in sequential read performance. Many users have been reluctant to adopt TLC SSDs. There was a good reason to wait when the technology first came to market, but modern TLC NAND is much better. The controllers that manage the flash are more powerful and have better error correction algorithms, which boost performance.
SanDisk's extensive experience with tuning Marvell controllers for high performance paid off with the X400 1TB. The drive is competitive in the sequential read portion of our review.
Sequential Write Performance
nCache 2.0 keeps sequential data writes moving at a high speed. The SLC cache buffer appears to flush the data quickly in our automated Iometer test. We didn't observe erratic behavior with any of the drives during the test. We used HD Tune Pro to write 128KB blocks across the full user LBA span of the drive, and the X400's native TLC write performance with this block size is right around 275 MB/s. It's not as fast as the Samsung 850 EVO 1TB, but it is faster than the first generation TLC-based products that came without direct-to-die algorithms.
Random Read Performance
The X400 1TB trails only the Samsung 850 EVO 1TB in the random read tests at a queue depth of 1. The drive doesn't surpass the 10,000 random read IOPS mark at QD1, but it comes very close. The X400 scales well all the way up to QD16. The performance regresses slightly at QD32, but you will never reach that intensity under normal use, or even during heavy multitasking unless you are using the drive for virtualization.
Random Write Performance
The X400 1TB delivers lower random write performance than the competition at every queue depth beyond QD1. The drive trails the Mushkin Reactor 1TB with MLC and Samsung 850 EVO with 48-layer TLC. The X400 slots in the middle of those two products at QD1, but quickly falls behind at higher queue depths.
80 Percent Sequential Mixed Workload
We describe our mixed workload testing in detail here, and describe our steady state tests here.
The SanDisk X400 1TB performs very well in our mixed workload sequential test, which is light enough that it does not push the drives down into steady state. At queue depths 2 and 4 (you can't have true mixed workloads at QD1), the X400 trails the Corsair Force LE 960GB and Crucial BX200 960GB by a small margin.
80 Percent Random Mixed Workload
The SanDisk X400 1TB trails only the Samsung 850 EVO 1TB during mixed random workloads until we reach very high queue depths. The X400 only trails the 850 EVO by a small amount in many of tests, so it will be interesting to see the real-world performance charts.
Sequential Steady-State
The SanDisk X400 1TB trails all but the Crucial BX200 960GB during most of the read/write mixtures used in the steady state test. The X400 is not the drive you want to use for write-heavy environments, such as editing high bit-rate video. The low endurance rating will keep most professional users from using the drive for this type of application.
Random Steady-State
Most power users wouldn't willingly choose two entry-level SSDs to use in RAID 0. The X400 1TB SSD delivers consistent 4KB random data writes, but the sustained level is much lower than the mainstream 850 EVO and most of the current crop of premium SSDs.
