History Of The External Hard Disk
The earliest external hard disk was gigantic. Possibly 100 times bigger than todays and only capable of holding just a few megabytes of data !. In those days data was held externally to the computer so it genuinely earned the name external hard disk. Due to the insufficient capacity these external hard disks were swappable so the large mainframe computer could have 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 computer systems running Windows, while external hard drives remained popular for much longer on the Apple Macintosh along with other professional workstations which provided external SCSI ports. Apple made such interfaces accessible 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 PC market as well. These new interfaces supplanted the more complex and costly SCSI interfaces, resulting in standardization and cost reductions for the external hard drive.
The inner framework of external hard disk drives resembles typical 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 jolts than flash-based technology (a fact often overlooked by consumers 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 generally carry a similar cost. More expensive models, especially drives with biometric security or several interfaces, usually cost significantly more per gigabyte. Smaller, portable 2.5″ drives created for laptop and embedded devices are a bit more expensive in cost per GB compared with 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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