Makes me wonder what would be the result of wiping all free space, which is the approach I like to use .....
After deleting unneeded filesm write zeros to a file and continue to write to that file until the partition fills up.
then delete the file returning all the free space again .... only now it is wiped of all previous content.
I imagine this would work just as well on SSDs as on HDDs.
My limited understanding of how they work,the ssd drive keep a certain sectors to itself,away from access from outside,when it notice a sector is going bad,it marks it as invalid and take a piece from its reserved space to replace it. This reserved space is also circulated to prevent it from being 100% unused while the "exposed" space is being over used.
So, you may, for example, create a file,delete it and the space of the deleted file may be taken to be part of the reserved space the file system has no access to and does not know it exists and overwriting the ssd multiple times will not overwrite the file because its in a location that can not be reached normally from outside.
Erasing a file on an ssd drive by conventional tools is not a guarantee the file is gone.