A total of 40 SSD products were listed in the evaluation, mostly MLC SSDs with capacities of 64GB and 128GB. In the evaluation, DRAMeXchane compared the differences between SLC NAND Flash and MLC SSD, as well as the differences between SSD controllers.

Of the many products in the evaluation, although some of the SSD controllers were supplied by the same vendors, different sources of NAND Flash also results in the differences in their performance. Another factor affecting the performance is the SSD firmware itself; each individual vendor has its own method of optimizing their firmware.

Nand Flash chips used in the SSD are divided into higher priced SCL and lower-priced MLC. The former is suitable for writing data, while the latter shows better performance in reading data; the downside of the MLC is its shorter life span and that it requires SSD controller to provide better algorithms to enable MLC SSD Flash chips to write data uniformly to extend its service life.

Theoretically, the current algorithm framework allows it to remain operational for a good few years. DRAMeXchange will also conduct tests to address concerns such as SSD performance decline after long-term use, or re-formatting required to restore its performance.

Reading performance of MLC SSD is generally good; reading speed of 200MB~260MB per second is already one of the most important requirements of SSD products in 2010.

As for writing performance, SLC SSDs are still faster, achieving >200MB per second. However, in this 1H2010 evaluation, there are also MLC SSDs that are capable of reaching writing speed of 200MB per second.

SSD Controller ICs Key to SSD Performance

In this evaluation, DRAMeXchange found out that in the efficiency of SSD controllers, in addition to Intel and Samsung's Flash which are produced in-house, others such as SandForce, Indilinx, JMicron also performed well.

Among them, SSDs featuring SandForce chip generally do not have built-in DRAM cache. The new design enables the SSD to rival against SSDs with DRAM cache and Indilinx, JMicron controller.

Overall Evaluation of SSD

As the writing time of Flash memory chips is limited to between thousand of times to ten thousand times, many may be concerned about the lifespan of Flash memory based SSDs. Considering this fact, manufacturers have adopted the algorithm which takes account of the storage times and detritions of different areas of the chip, and have established the balanced quality subject to the written data, preventing the over-writing of specific zone of the chip.

The SSD also features data-preservation during power failure, coupled with wear leveling technology, users can be more assured of the data security.