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).
Manta rays are largest rays in the world, with wingspans reaching 7 metres. They have one of the highest brain-to-body mass ratios of all fish. Manta populations suffer when they are caught as bycatch by fishermen fishing for other species, but fisheries which target manta rays are even more harmful.