Serial ATA Flash Drive

APS25M5Xxxxx-PXX

9

© 2013 Apacer Technology Inc.

Rev. 1.5

3.6

TRIM

TRIM, though in capital letters usually, is a memory computation command rather than an abbreviation. It is

mainly a SATA command that enables the operating system to inform the SSD (Solid State Drive) which

blocks of previously stored data are no longer valid, due to erases by the host or operating system, such as

file deletions or disk formatting. Once notified, SSD will begin the discard of the invalid LBAs and retain more

space for itself, in fact, the discarded is no longer recoverable.

When an LBA is replaced by the operating system, as with overwrite of a file, the SSD is informed that the

originally occupied LBA is determined as no longer in use or invalid. The SSD will not save those blocks in

garbage collected sectors. Noticeably, a file deletion command by host or operating system never actually

erases the actual content, rather, just the file is marked as deleted. This issue is even specifically noticeable

for flash based memory devices, such as SSDs. In fact, an SSD will keep garbage collecting the invalid,

previously occupied LBAs, if it is not informed that these LBAs can be erased. Thus, the SSD would

experience a significant performance downfall.