by Robert Tanner on July 29, 2013 in Solid-State Drives
Enthusiast SSDs may get all of the fame and glory, but it’s the value brands that always sell the most drives. As a relative newcomer that doesn’t rely on SandForce controllers like many other vendors do, can SanDisk’s Marvell-equipped Ultra Plus deliver that “Ultra” good value we’re looking for?
Many of our readers should find the SanDisk name to at least be familiar, as the company has been a long time market-leader of flash memory products, offering just about every type of memory card imaginable, flash drives and even flash-based music players. As these products deal exclusively with NAND flash memory, it shouldn’t be any surprise that solid-state drives would be a natural progression for SanDisk to take. In fact, it’s been in the SSD market for some time with a full portfolio of enterprise SSDs, from SAS to PCie, along with SSD caching solutions.
The company doesn’t just build the products, but also the NAND itself. SanDisk shares a joint venture with Toshiba on several NAND fab facilities very similar to the Intel/Micron IMFT arrangement, which is important to note for several reasons. Producing NAND directly means SanDisk isn’t subject to market prices for NAND flash (which cuts down on costs), and it can strictly regulate the quality of the NAND it produces and reserve the best bins for its in-house SSD products.
||SanDisk Ultra Plus Solid-State Drives
||Marvell SS889175 4-Channel
||SanDisk 19nm eX2 ABL MLC
|Random Read (IOPS)
|Random Write (IOPS)
||SATA 3.0 (6Gbps)
The SanDisk SSD we’re looking at is the Ultra Plus, the value alternative to the recently-launched Extreme II family. The Ultra Plus isn’t another SandForce clone; instead, it’s powered by a Marvell SS889175 4-channel controller, making its pedigree a close relative to Intel’s 510 family of SSDs – but with an interesting twist. The Ultra Plus is a 7mm height SSD utilizing SanDisk’s own 19nm eX2 ABL MLC NAND. The mouthful of a name is due to a little “special sauce” SanDisk labels “nCache” technology.
SanDisk’s nCache is where a small section of the MLC flash is set aside and effectively operates as an SLC fast-write cache. This uniquely SanDisk design allows the Ultra Plus to be unusually responsive to random writes despite its 4-channel controller, with the nCache performing a sequential write to the main MLC flash after-the-fact.
For readers wondering why the SSD’s DRAM cache isn’t used in this function, remember that in the event of a sudden power loss, any data residing in the DRAM could be lost before it can be written to the NAND flash. SanDisk’s solution elegantly avoids this problem entirely by caching to the NAND instead. In the event of a power loss, the data in the nCache will be written out to the SSD’s main flash storage upon the next boot. The size of area reserved for SanDisk’s nCache is likely close to the size of the spare area of the SSD itself, up to a few gigabytes – much larger than the onboard 128MB DRAM cache.