I have a laptop with two x Intel SSD drives in RAID0, giving around 5-600MB/s write performance. Everything is pretty fast, but when i try to wipe free space, the progress text/bar will within 5-7% start to slow down more and more, so "Wife MFT Free Space" will never continue.
Sometimes this happens as soon as it start, other times it goes fine for the first 5%, before slowing down.
This happens even with single overwrite (one pass)
I would go one step further and remove 'really' from Winapp2's point.
"you should NOT run Free Wipe Space on a SSD..."
and for that matter, it can be dumbed down further to "don't do anything to a SSD that is User controlled - let the OS (only) look after it"
of course, if you know about the limited life cycles of SSD memory cells and either aren't worried, or money is no option or don't have any mechanical drives, then you can/have to do whatever you want.
WinnApp2.ini has it right. Wipe Free Space is a security feature and can take hours if not days to complete. It writes over "deleted" areas on your hard drive to erase what was once there, since with Windows pressing delete doesn't really delete anything. It just marks the space as available, but the data is still there, just incaccessible to people without skill or special programs to retrieve the information.
I used Wipe Free Space once and that was the last time I ever used it.