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The four models all target slightly different sectors: the top-end CloudSpeed Extreme is aimed at large databases such as are used in high volume online transaction processing environments, and as such is rated for up to ten full drive rates per day. CloudSpeed Ultra, rated for up to three full drive writes a day with mixed read/write workloads, is aimed at applications such as email servers where read demands typically outweigh writing, but not by much. CloudSpeed Ascend suits more read-intensive usage at a rate up to one full drive write a day, while the device we had for review, the CloudSpeed Eco, targets much the same use case but at a more economical level, and is also rated at up to one full drive write per day. The CloudSpeed Eco despite being the entry level model in the range still offers a sequential read/write speed of up to 475/450 MB per second, and a highly impressive random read-write rate of up to 80k/14k IOPS.

The key distinction between the CloudSpeed Eco and its 'big brothers' is that it offers a (slightly) lower level of over-provisioning, and is sold with a three-year warranty compared to the five years offered on the Extreme, Ultra and Ascend versions. The Eco model is available in capacities of 240GB to 960GB (we tested the 480GB version). All of the drives offer the same 6GB/s SATA interface and 2.5 inch form factor, and employ SanDisk's 19nm MLC NAND flash. As has been touched on in the article elsewhere in this issue on flash wear, smaller NAND means more chips per wafer and thus more useable storage, but can impact the amount of charge stored per cell, and ultimately shorten the life of the drive.

SanDisk approaches this issue with its proprietary Guardian technology platform, which it claims can even reduce TCO by providing greater endurance and data integrity, as well as protecting against power loss problems. SanDisk boasts that the CloudSpeed Eco delivers up to five times higher endurance than rival MLC SATA SSD offerings - a claim hard to disprove without intensive long-term testing, but there's no question that the technology is proven.

The Guardian platform comprises three distinct technologies:

FlashGuard: combines Aggregated Flash Management, which treats all flash elements as a single system, and Advanced Signal Processing, which dynamically adjusts flash parameters throughout the life of the SSD, to reliably extract significantly more life from cost-effective 19nm MLC flash;

DataGuard: features full data path protection, safeguarding user data from corruption along all data paths in the SSD

EverGuard: protects against loss of user data in the event of unexpected power interruptions using what SanDisk describe as a '3rd generation backup power circuit design and high-reliability discrete capacitors'.

The real benefit comes from the fact that SanDisk themselves own the flash as well as the tools built into the drive, so there is a level of vertical integration across all the product's features that some other SSD drive vendors might struggle to match. The Guardian technology and the NAND itself have been designed to work seamlessly together to deliver high performance and reliability.

Product: CloudSpeed Eco SATA SSD
Supplier: SanDisk
Web site: www.sandisk/enterprise