@אלי-TZA וכאן (עם יותר הסבר..): https://www.digitalcitizen.life/simple-questions-what-trim-ssds-why-it-useful
וכאן
(מויקי: SSDs store data in flash memory cells that are grouped into pages typically of 4 to 16 kB, grouped together into blocks of typically 128 to 512 pages. Example: 512 kB blocks that group 128 pages of 4 kB each. NAND flash memory cells can only be directly written to when they are empty. If they may contain data, the contents must be erased before a write operation. An SSD write operation can be done on a single page but, due to hardware limitations, erase commands always affect entire blocks; consequently writing data to empty pages on an SSD is very fast, but slows down considerably once previously written pages need to be overwritten. Since an erase of the cells in the page is needed before it can be written again, but only entire blocks can be erased, an overwrite will initiate a read-erase-modify-write cycle: the contents of the entire block are stored in cache, then the entire block is erased from the SSD, then the overwritten page is written to the cached block, and only then can the entire updated block be written to the flash medium. This phenomenon is known as write amplification.)
