SanDisk Ultra Plus 256GB SSD Review
The SanDisk Ultra Plus features SanDisk's proprietary eX2 ABL MLC NAND with nCache technology. This technique creates a SLC layer to help boost write performance and enhance endurance. The SSD also features a four channel Marvel 88SS9175 controller and 128MB of DRAM cache.
SanDisk Ultra Plus 256GB SSD Basics
SanDisk, one of the worlds largest NAND fabricators, has released the SanDisk Ultra Plus SSD. This SATA 6Gb/s SSD boasts speeds of 530MB/s in sequential read and 445MB/s in sequential write speed. For the 256GB version we are reviewing today the SSD also delivers 82,000 random read IOPS and 39,000 random write IOPS.
This performance is provided in part by SanDisk's new 19nm eX2 ABL MLC NAND which is manufactured internally in a strategic alliance with Toshiba. Dubbed 'Flash Forward', this venture between the two giants weighs in as the world’s second largest flash producer, providing 24.7% of the world’s supply of NAND. This provides SanDisk with access to its own NAND, and with its own DRAM integrated into the SSD SanDisk can build much of the product in-house.
SanDisk and Toshiba have jointly engineered the new ABL (All Bit Line) architecture for the 19nm NAND. ABL can deliver up to twice the parallelism in comparison to typical HBL (Half Bit Line) NAND. This new technique is geared to deliver enhanced performance and endurance for this new generation of NAND.
The only key component that SanDisk lacks is its own controller technology for the consumer SSD market. The controller is the engine of the SSD and is the most important component. For the controller aspect SanDisk has traditionally turned to an outside vendor, LSI SandForce, to provide its controller technology. The previous generation SanDisk Ultra was powered by the SF-1200 controller, and the SanDisk Extreme, reviewed here, features the SF-2281 controller.
The Ultra Plus marks the diversification of SanDisk's product line with the adoption of the Marvell 88SS9175 controller. This provides SanDisk with another option for its customers, and the flexible nature of the Marvell firmware gives SanDisk the ability to customize the characteristics of the SSD.
The pairing of custom SanDisk firmware and the 19nm eX2 ABL MLC NAND has lead to "nCache," a new caching approach for the Ultra Plus SSD. This new approach uses an 'SLC-layer' programmed into the MLC NAND, utilizing this as a non-volatile cache to enhance the write endurance of the SSD. This approach has paid dividends in the form of an 80 TBW (Terabytes Written) rating.
Another focus during the design of this SSD is to serve the mobile market as well as typical desktop users. This lead to the utilization of the four channel Marvell 9175. This four channel version of the more powerful 8- channel Marvell 9187 controller brings very conservative power consumption figures that are well suited for mobile environments.
In a brutally competitive SSD market it is somewhat risky to make significant performance trade-offs in favor of power consumption. The key is to balance the power consumption without losing performance, and this is accomplished by utilization of ultra-low power states that consume only .08 Watts during 'Slumber.' Active power is rated at a low .12 Watts, which we will test later in the review.
The problem of utilizing a four channel controller is that the resulting loss of parallelism often leads to lower performance than other SSDs featuring more channels. This brings a tough decision between bleeding edge performance and sensible power consumption. With good performance and great power consumption in concert with aggressive pricing SanDisk may come out with a winning combination.