Originally Posted by Suijin
Actually they can according to PC Per, you can't defrag an SSD currently. You can defrag a regular hard drive to reclaim the performance.
You don't need to defrag an SSD because file fragmentation does not affect sequential or random reads. Free space fragmentation, however, is said to degrade SSD random write performance, and free space consolidation is said to help reclaim performance when it deteriorates after a few months/weeks of use (except for the X-25).
BTW, the fragmentation you see in the X-25 is unrelated to file fragmentation; instead, I believe, it is a result of the wear-levelling mechanism of the drive which is different from other SSDs.