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 reef manta is smaller than the oceanic manta ray, with an average disc-width of 3-3.5 metres (9-11.5ft) and a possible maximum of 4.5 metres (15ft). Itâs likely at such sizes reef mantas would weigh in at around 1.4 tonnes (3,100 lbs). All mantas start off small, so size is not necessarily a good identification feature. The dorsal shading and ventral spot patterning however can be used to discern between these two species.