SSD TRIM : why can't the drive initiate this itself?

tmpc1066

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I am trying to understand the whole TRIM / Garbage Collection thing and have read numerous places that the reason TRIM is needed is because the SSD itself doesn't know which files have been deleted. So, if the drive doesn't know what it contains, how can I remove a drive from one computer, connected it to another, and see everything? The answer has to be that the drive does, in fact, know what files it contains. So, if it contains that information, why can't the drive itself initiate TRIM when it sees that a file has been deleted?
 
Solution
It's not that SSD's don't which files have been deleted. It's very aware of which files have been deleted. The problem is that during a single operation a SSD can only read,write or delete, it can't rewrite like a traditional HDD.

So when a SSD deletes a file it marks the file as deleted. All new data is written around the files marked deleted. Eventually the SSD run out of room entirely and performance drops drastically. The SSD must first erase a file, then perform a write over it. TRIM is what actually erases the files marked for deletion during the SSD's idle time as to not bother the user. The drive doesn't do it automatically because it doesn't really know when the user is idle. It leaves that to the OS. Windows 8 and...
It's not that SSD's don't which files have been deleted. It's very aware of which files have been deleted. The problem is that during a single operation a SSD can only read,write or delete, it can't rewrite like a traditional HDD.

So when a SSD deletes a file it marks the file as deleted. All new data is written around the files marked deleted. Eventually the SSD run out of room entirely and performance drops drastically. The SSD must first erase a file, then perform a write over it. TRIM is what actually erases the files marked for deletion during the SSD's idle time as to not bother the user. The drive doesn't do it automatically because it doesn't really know when the user is idle. It leaves that to the OS. Windows 8 and 10 do a pretty good job doing it in the background.
 
Solution

tmpc1066

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I see. Does background Garbage Collection eventually erase these deleted files?