Understand SSD

• page 01: Flash memory
• page 02: MLC and SLC
• page 03: Sectors, pages, blocks...
• page 04: Wear-leveling
• page 05: TRIM
• page 06: Garbage collector
• page 07: Every day usage
• page 08: Conclusion

In the last firmware updates dedicated to its Vertex series, OCZ introduced a new function known as Nand Launderer.

It could be an algorithm allowing optimization of performances in writing mode during low request load period. It could use a system similar to the one known as "garbage collector" in some programing language or high-end scientific calculator from Texas Instrument (TI-89 for example).

During inactive periods, the SSD reorganizes data in order to optimize future writing procedures. As we mentioned, earlier SSDs offer higher performance levels in sequential writing mode than in random mode. To improve performance, one would need to transform random steps into sequential steps. It can be achieved by taking advantage of the erasable status of pages: during low request load period, the controller will transfer data from blocks to other blocks in order to turn as many blocks as possible into fully-erasable status. This process is relatively similar to the defragmenting program in its concept, even though unlike disc-based HDD, the logical structure does not correspond to the physical structure.

New generations of SSDs from Samsung (such as Samsung PB22-J, OCZ Summit, Corsair series P) and Intel could integrate such technologies, and thus could maintain optimal performance levels over time, despite the lack of the TRIM command.