Flash is digital computer memory that is erased and re-written by electrical signals. There are two main types of flash memory named after NAND and NOR logic gates. When referring to USB Flash drives, NAND is the most common logic gates used for data storage and transfer. Here is a quick overview of the three types of NAND Flash memory chips.
Single Layer Cell (SLC)- this type is only capable of holding one bit per cell. The SLC has a fast writing speed and is good for industrial use and holding critical data.
Multi Layer Cell (MLC)- the multi layer cell can hold twice as much information. The MLC is used mostly in consumer products because it is less expensive than the single layer.
Triple Layer Cell (TLC)- while it holds three bits per cell and has the lowest cost, the TLC has slower reading and writing speeds. This type is found in low end products and is not recommended for storing critical data.
Keep in mind that the older your flash drive gets, the less reliable it becomes. NAND Flash memory loses the ability to retain date after thousands of writing and erasing cycles, this refers to the flash drives endurance.
Another specification to keep in mind is the retention of the Flash. Retention expresses how long the flash memory cells will maintain its programs without power. Taking care of your flash drive- especially keeping it out of high temperatures- will conserve the flash’s capability to retain.