- Flash drive does not work like a hard disk. There is no read/write head exist. Therefore, no matter where the data is save, it will not burdened the flash drive.
- There is a limit in the number of time that you can write to your flash drive. Defrag process involves read and write. As a consequence, your flash drive will die sooner.
So, don't waste your time defragging the flash drive. Save it for your hard drive.
note: This article shows how long does a flash drive will last.