For a hard drive, defrag is GOOD.
For an SSD, defrag is BAD.
Simply put defrag places data in order for faster reading and less head travel.
Since SSD's have near instant access and have to move data across the flash in a way that reduces the chance of wearing out a section(allows the drive to last longer by using ALL flash evenly) the location Windows thinks has the data does not actually contain the data on an SSD. only the SSD controller knows the location of all data. An SSD can look all fragmented, while in fact the controller may have organized the actual data into its most efficient form already.
Running defrag does not KILL an ssd, just uses write cycles that the ssd has a limited number of. So if you did defrag an ssd, it...