Reply 40 of 78, by Doornkaat
From what I can gather TRIM is performed when an OS that supports TRIM deletes a file on an SSD that supports TRIM marking the block irrelevant so it won't be reallocated/rewritten upon next GC. (Controller doesn't know what data is valid/invalid, only discerns between empty/used blocks and once written will preserve any data except if OS tells it to overwrite a block or - via TRIM - tells it this block no longer contains valid data after deletion.)
That means TRIM has to be done when a file is deleted and can't be done afterwards.
If you want to TRIM a drive that's used with a non-TRIM OS the only way is to write data to all free space, then delete it on the TRIM OS.
Did I get that right?