Flash

SSD TRIM Marks Unused Data for Controller Reclamation

Deleting a file changes filesystem metadata, but an SSD does not automatically know that every flash page formerly associated with the file can be treated as disposable. From the drive’s point of view, previously written logical block addresses can remain valid until the host explicitly indicates otherwise or overwrites them. TRIM provides that indication for ATA storage. Comparable deallocation commands exist in other storage protocols. The host identifies logical block ranges whose previous contents no longer need to be preserved, and the SSD can use that information when managing flash internally.