These days, we rarely get to discuss a SSD that uses all Single-Level Cell (SLC) flash. Even on the enterprise side, SLC is the golden egg that only shows up from time to time, and only in products designed for extreme workloads. Multi-Level Cell (MLC) flash has ruled the roost for several years, and projections show that Triple-Level Cell (TLC) will soon rapidly gain market share from MLC.
SLC flash only writes half as much of the data to the flash as MLC. With SLC, things are simplified, and the data will only be a one or a zero. In terms of capacity, that means SLC needs twice as many NAND die per drive than a MLC part. Since the base cost comes from a wafer that is cut into flash die, and is then packaged for use on a SSD, a SLC SSD will have to cost at least twice as much as a MLC SSD.
When we first tested a modern SLC SSD, the price was a larger issue since the density was limited to 128GB at a time when 256GB SSDs were popular. At the time, the 128GB SLC drive cost more than a 256GB SSD around $275. Still, those lucky enough to purchase the SuperSSpeed S301 based drives were rewarded with lasting performance that didn't slow over time, and industry leading endurance.
In terms of endurance, SLC lasts for around 100K program / erase cycles. To put that into perspective, we went on and on about Samsung's new 3D V-NAND technology, and how backroom conversations led us to believe the new technology had around 35K PE cycles. Typical MLC flash shipping today is rated for 3K PE cycles, but that can range from 1.5K to 10K depending on the product. TLC flash ranges from 800 PE cycles to 1.5K, so the leap from MLC and TLC standards to SLC standards is significant.
SLC flash also needs less time to read and write data than MLC or TLC flash. Caching techniques from Samsung, SanDisk, and most recently, Micron, allow a drive to write small bursts to the flash as it would to SLC by manipulating the flash translation layer. This is an excellent method to increase write performance for a short period of time. For most consumers, the short burst is more than enough to increase performance for day-to-day activities. Although, performance slows when a user has written to the SLC area, and the data writes are then forced to the MLC, or worse, the TLC flash at their native speeds. Heavy workload environments that push data at high speeds to a SSD, like editing a large video, can fill the SLC buffer, and then slow by as much as two-thirds when completing the task.
The way around this for professional environments is to simply move to all SLC flash, rather than just a small amount of SLC like flash in a product.
Specifications, Pricing, and Availability
Fujitsu is a world leader in enterprise storage technology, and entered the consumer SSD market around June 2014. We've already published a report of the F100, a mainstream consumer focused MLC SSD that uses controller technology from Silicon Motion. We also took an early look at the Quadro-M, an All-in-One RAID PCIe product.
Today we're looking at the Fujitsu FSXtreme 240GB, which uses a SandForce SF-2281 controller, and 25nm Intel SLC NAND flash. The flash in the FSXtreme is a bit different from the SLC flash used in the SuperSSpeed products from a few years ago. The flash now features 16KB page sizes; the S301 used 8K page sizes. The new 25nm Intel SLC allows Fujitsu to package up to 256GB of raw SLC flash in a single SSD.
The FSXtreme is available in three capacities, 60GB, 120GB, and 240GB; these are all overprovisioned sizes so 64GB, 128GB, and 256GB flash are actually present, but hidden from the user. The reserved OP area handles background activities like garbage collection and wear leveling, even when the drive's user capacity is full.
The FSXtreme uses a SandForce SF-2281 controller for all three capacities. In our tests with the SuperSSpeed S301 128GB and 120GB models, we observed similar performance with compressible and incompressible data. The same carries over to the Fujitsu FSXtreme. The SLC flash virtually removes the number one drawback of SF-2281 products, although, the incompressible performance slowdown is often only observed while running benchmark software.
Fujitsu attached a full five-year warranty to the FSXtreme products. In the U.S., purchasing a drive isn't as easy as ordering from Amazon or Newegg; this is an area Fujitsu is working on, and we may see Fujitsu branded products on Amazon shortly. At this time, Fujitsu has led us to one of the company's partners who accepts international orders, and provides quick shipping. You can purchase the Fujitsu FSXtreme 240GB for $228.80 USD from this link, and expect delivery within a few days. The FSXtreme 120GB model sells for $130.79 USD.
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- Page 1 [Introduction & Specifications, Pricing, and Availability]
- Page 2 [Fujitsu FSXtreme 240GB SLC SSD]
- Page 3 [Test System Setup and Initial Performance]
- Page 4 [Benchmarks - Sequential Performance]
- Page 5 [Benchmarks - Anvil Storage Utilities]
- Page 6 [Benchmarks - Mixed Read / Write Workloads]
- Page 7 [PCMark 8 Consistency Test]
- Page 8 [PCMark 8 Consistency Test - Continued]
- Page 9 [Benchmarks - Power Testing and NAS Cache]
- Page 10 [Final Thoughts]