Portable+hard+Disks

History The first commercial hard disks were largeand were not stored within the computer itself, and therefore fit within the definition of an external hard disk. The hard disk platters were stored within protective covers or memory units, which sit outside. a olden portable hard disk mounted on a CRT screen 

Structure and design

These hard disks soon were able to be compact enough that the disks were able to be mounted into bays inside a computer. Early Apple Macintosh computers did not have easily accessible hard drive bays. Early external drives were not as compact or portable as their modern descendents. By the end of the 20th century, internal drives became the system of choice for computers running Windows, while external hard drives remained popular for much longer on the Apple Macintosh and other professional workstations Apple made such interfaces available by default from 1986 and 1998.

The internal structure of external hard disk drives is similar to normal hard disk drives; in fact, they include a normal hard disk drive which is mounted in a disk enclosure. In a 2009 Computer Shopper comparison of 5 top external hard drives, the capacities ranged from 160 GB to 4TB. External hard drives retain the platters and moving heads of traditional hard drives they are much less tolerant of physical shocks than flash-based technology More pricey models, especially drives with biometric security or multiple interfaces, generally cost considerably more per gigabyte. Small MP3 players, previously built around mechanical hard drive technology are now primarily solid state CompactFlash based devices.

Compatibility Modern external hard drives are compatible with all operating systems supporting the relevant interface These standards are supported by all major modern server and desktop operating systems and many embedded devices.

A portable hard disk connect to a laptop