I'm washing some 1TB drives after deleting some user profiles from them. I want to keep the Windows installed on them.

With most of the space empty, this is going to take several hours each, yet most of that space has never been used and doesn't need washing. Is it possible for Ztree to know which blocks have been used, and just wash those? Or is there no way for Ztree to distinguish them from the unused ones?

Or given Ztree's technique of just creating a big file, is this kind of thing out of the question altogether?