The movement of the hard drive's read/write heads over different areas of the disk when accessing fragmented files is slower, compared to accessing the entire contents of a non-fragmented file sequentially without moving the read/write heads to seek other fragments.
The dorsal fins are small and at the base of the tail. The largest mantas can reach 1,350 kg (2,980 lb). In both species the width is approximately 2.2 times the length of the body; M. birostris reaches at least 7 m (23 ft) in width while M. alfredi reaches about 5.5 m (18 ft).
The manta ray (Manta birostris) is the largest ray reaching up to 9 meters in width. This ray feeds on plankton and small fish and are completely harmless to humans. The common skate (Dipturus batis) is the largest skate in the world, reaching up to 250 cm in length with a life span of approximately 50 years.