External storage

Data storage outside a computer's own hardware

In computing, external storage refers to non volatile (secondary) data storage outside a computer's own internal hardware, and thus can be readily disconnected and accessed elsewhere. Such storage devices may refer to removable media (e. g. punched paper, magnetic tape, floppy disk and optical disc), compact flash drives (USB flash drive and memory card), portable storage devices (external solid state drive and enclosured hard disk drive), or network attached storage. Web based cloud storage is the latest technology for external storage.

Today the term external storage most commonly applies to those storage devices external to a personal computer. The terms refer to any storage external to the computer. Storage as distinct from memory in the early days of computing was always external to the computer as for example in the punched card devices and media. Today storage devices may be internal or external to a computer system. In the 1950s, introduction of magnetic tapes and hard disk drives allowed for mass external storage of information, which played the key part of the computer revolution. Initially all external storage, tape and hard disk drives are today available as both internal and external storage. In the 1964 removable disk media was introduced by the IBM 2310 disk drive with its 2315 cartridge used in IBM 1800 and IBM 1130 computers. Magnetic disk media is today not removable; however disk devices and media such as optical disc drives and optical discs are available both as internal storage and external storage.

As a consequence of rapid development of electronic computers, capability for integration of existing input, output, and storage devices was a determinant factor in their adoption. IBM 650 was a first mass produced electronic computer that encompassed wide range of existing in technologies for input output and memory devices, and it also included tape to card and card to tape conversion units. Earlier "transportable personal storage" was introduced by IBM's 2315 disk cartridges, which were used in IBM 1800 and IBM 1130 computers. Operating systems of the earlier 1960s provided a general purpose file system for external storage, which included hierarchical directories, symbolic links, and access control to time sharing mainframe computers. Some of such earlier examples include UNIVAC, MULTICS, and UNIX.

Optical storage devices have media that use laser light technology for data storage and retrieval.

DVD stands for Digital Versatile Disc. Its speed is much faster than CD but not as fast as hard disk. The standard DVD 5 technology has a storage capacity of 4.7 GB per layer; most DVDs have a single layer but up to four layers are specified. Also DVD storage capacity changes with recording format.

Blu ray storage capacity is up to 50 gigabytes (or even 100 GB) of data. and less power consumption.