jmke

It has been approximately three years since flash-memory based storage drives became accessible to the normal citizen. I remember that in the netbooks debut, many were running Linux distributions from small SSDs, typically in the 16GB range. One could mention here the ASUS Eee PC 701, the pioneer of all netbooks. Then, we have seen these more expensive models being equipped of SSDs in the 40GB range, available with either Linux or Windows XP. Later came the netbooks with mechanical hard drives in the 80 or 160GB format which, looking at today's offerings, have dominated the market. I still think however that the first netbooks equipped of small SSDs have made a step forward the adoption of flash-based storage in the market. It is due to them if today the term SSD is known by almost all people which computers are in their field of interest. I although would not call this an adoption yet since only a portion of the enthusiasts, being a very tiny portion of people in general, now possess an SSD.

However I now think the technology has matured enough. At first, some had doubts about the long-term reliability. It is not until recently that the first TRIM enabled drives hit the market, resolving performance loss over long-term usage. The TRIM command basically consists of letting the drive controller know which memory cells are no longer in use, so that it can delete its content. (The file system does not do that; it just marks it as unused, but keeps data stored in it.) This has to do with the fact that SSDs have to delete an entire NAND memory block, whereas they can read or write at the cell level. As long as there are free memory cells, it will be able to write data in them at full speed. When all memory cells have been used at least once and not "trimmed", this is where the slowdown will show up. When the drive will want to write data, it will first have to copy the whole NAND memory block to cache and modify its data. Next step is to delete the actual memory block on the drive, and write the modified one from the cache to the memory block. That means it gets to manipulate lots of data for maybe just a few bits. This is why the TRIM function will keep an SSD as fast as it was by telling the drive controller to actually erase the data in the specified cells so that some other data can be written as if the cells were never used.

http://www.neoseeker.com/Articles/Ha...ews/torqx_128/

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