HotHardware has an article about garbage collection for SSD drives. They start with a summary of why this process is of vital importance:
The flash memory used on today’s SSDs is comprised of cells that usually contain 4KB pages that are arranged in blocks of 512KB. When a cell is unused, data can be written to it relatively quickly. But if a cell already contains some data–no matter how little, even if it fills only a single page in the block–the entire block must be re-written. That means, whatever data is already present in the block must be read, then it must be combined or replaced, etc. with the new additional data, and the entire block is then re-written. As you can surmise, this process takes much longer than simply writing data straight to an empty block.
They managed to get their hands on a new SSD from OCZ that includes new firmware for the Indilinx controllers used on their drives; this new firmware will automatically do garbage collection while the drives are idle. The additional write cycles will slighty shorten the lifespan of the drive, but it does improve performance! Some examples of their benchmark results below, read the full article for more:
In other news, OCZ’s 1TB SSD is due to be released later this month. This is a a rather interesting unit: it will consist of several smaller drives, packaged in a 3.5 inch enclosure together with a RAID-controller. When used in RAID-0 mode, it’s fast enough to almost saturate a 3Gbps SATA-connection, with read and write speeds of over 200 MBps.