I've recently purchased a used Crucial m4 128GB SSD. I did a windows format on the SSD and the usable space is only 106 gb. I understand that there are "reserved space" but ~22 gb seems awfully alot. Maybe these are shadow copies from the previous owner? I've never used a ssd before but is this normal? Any ways to free up more space? I have installed OS on it already so I would prefer not having to wipe the entire drive again.
SSDs have a dedicated amount of spare area that isn't usable or recoverable by the user. 22GB does seem a bit high, but as an example, my Samsung 830 256GB SSD only has 238GB usable.
It's also possible that since this is a used SSD that one or more of the NAND chips is no longer usable. NAND can only be written to/erased a finite number of times before it no longer functions. Although this is unlikely, the possibility is there.
Firstly, as I know, the SSD card always has no such capacity as it is marked. For example, 1GB SSD generally has only 1000KB, not 1024 KB in theory. Therefore, this can be one of the reasons for the difference.
Secondly, since your drive is used by others before, part of its capacity cannot be used, such as some bad sectors or chips.