High Quality Content by WIKIPEDIA articles! Higher performance in hard disk drives comes from devices which have faster performance characteristics. These devices include those with rotating media, hereby called rotating drives, i.e., hard disk drives (HDD), floppy disk drives (FDD), optical discs (DVD-RW / CD-RW), and it also covers devices without moving parts like solid-state drives (SSD). For SSDs, most of the attributes related to the movement of mechanical components are not applicable, but the device is actually affected by some other electrically based element that still causes a measurable delay when isolating and measuring that attribute. These performance characteristics can be grouped into two categories: access time and data transfer time (or rate).