It’s common practice for many computer owners to defragment their hard drives on their laptops and desktops. And for HDDs, it’s actually a very good practice – you conserve space on your drive and, especially, speed it up.
However, you should never, ever defrag your SSD – that is, unless you want it to fail way before its time.
Here’s what happens when you defrag a drive. When saving a large file, your system may choose to break up – fragment – that file into different sections of a hard drive. As a result, over time many files may be in different fragments throughout a hard drive. Due to the relatively long time frame an HDD takes to find all those pieces and put them back together, a heavily fragmented drive can create some major performance issues. Hence, the need to defrag: the drive finds all the fragmented files and reassembles them into nice, neat, single pieces on your drive, thus resulting in a performance improvement, especially for older drives with heavily fragmented files.
However, the seek time (the amount of time it takes to find a complete file) is vastly lower on SSDs than on HDDs. Defragging an SSD isn’t going to deliver a speed increase. In addition, realize that SSDs, over time, can wear out – it only has so many write cycles before the drive basically burns up. And as anybody who has ever defragged a drive can tell you, the defrag process means the disk is written to over and over and over…
In short: defragging an SSD uses up a lot of limited write cycles really quickly, and delivers no real improvement in performance. So you’re better off not doing it.