Back Ground Of The External Hard Disk
The original external hard disk was huge. More than likely 100 times bigger than todays and only capable of holding just a few megabytes of data !. At that time information was held externally to the computer so it definitely earned the name external hard disk. Due to the lack of capacity these external hard disks were swappable so the large mainframe computer could gain access to much more data.
The External hard Disk These days
By the end of the 20th century, internal drives took over as the system of choice for computers running Windows, while external hard drives continued to be common for much longer on the Apple Macintosh along with other professional workstations which provided external SCSI ports. Apple made such interfaces available by default from 1986 and 1998. The addition of USB and Firewire interfaces to standard personal computers led these types of drives to become commonplace in the Desktop market as well. These new interfaces supplanted the more complicated and high-priced SCSI interfaces, bringing about standardization and cost savings for the external hard drive.
The internal framework of external hard disk drives resembles normal hard disk drives; in fact, they include a normal hard disk drive which is mounted in a disk enclosure. For an external hard disk now the capacities range from 160 GB to 4TB and the cost per gigabyte varies between .15 and .40 USD.
As an external hard disk keeps the platters and moving heads of conventional hard drives they are much less tolerant of physical shocks than flash-based technology (a fact often overlooked by people lulled into a false sense of ruggedness by their styling).
Larger models often include full-sized 3.5″ PATA or SATA desktop hard drives, can be purchased in the same size ranges, and typically carry a similar cost. More expensive models, particularly drives with biometric security or several interfaces, usually cost significantly more per gigabyte. Smaller, portable 2.5″ drives intended for laptop and embedded devices are slightly more expensive in cost per GB in contrast to larger capacity 3.5″ drives. Small MP3 players, previously built around mechanical hard drive technology are now primarily solid state CompactFlash based devices.
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