The way I understand it, it’s an automated job that sends the “trim” command to SSDs to discard all the blocks that have been marked as unused by the filesystem. My knowledge is a little patchy so I’m probably missing some important details…
When you go to delete something on an SSD, it’s simply just marked as being deleted. The file still technically occupies space on the SSD and the SSD will never simply overwrite space that has a deleted file on it.
So… by enabling the service, systemd will automatically send the trim command that tells the SSD to empty out all the space occupied by files marked as deleted which allows the SSD to reuse said space.
The way I understand it, it’s an automated job that sends the “trim” command to SSDs to discard all the blocks that have been marked as unused by the filesystem. My knowledge is a little patchy so I’m probably missing some important details…
When you go to delete something on an SSD, it’s simply just marked as being deleted. The file still technically occupies space on the SSD and the SSD will never simply overwrite space that has a deleted file on it.
So… by enabling the service, systemd will automatically send the trim command that tells the SSD to empty out all the space occupied by files marked as deleted which allows the SSD to reuse said space.