The TRIM command helps to maintain the performance of solid state drives (SSDs) at an optimal level over the lifetime of the drive. TRIM functions by actively deleting invalid data from the SSD’s memory cells to ensure that write operations perform at full speed. Since a memory block must be erased before it can be re-programmed, TRIM improves performance by pro-actively erasing pages containing invalid data, allowing the SSD to write new data without first having to perform a time-consuming erase command.

EXAMPLE:

    SSD pages contain no data.
    User writes data to SSD pages.
    User deletes some data. Pages are marked as "not in use" by the OS, but data remains on SSD.
    TRIM command tells SSD controller that pages contain invalid data. Pages with invalid data are cleaned.
    Data is written back to SSD memory cells. The invalid data had been cleaned and data is able to be written to the pages at full speed.

The Trim command is designed to enable the operating system to notify the SSD which pages no longer contain valid data due to erases either by the user or operating system itself. During a delete operation, the OS will both mark the sectors as free for new data and send a Trim command to the SSD to be marked as no longer valid. After that the SSD knows not to relocate data from the affected blocks during garbage collection. This results in fewer writes to the flash, reducing write amplification and increasing drive life.