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- In 1953, IBM recognized the immediate application for what it termed a "Random Access File" having high capacity and rapid random access at a relatively low cost. After considering technologies such as wire matrices, rod arrays, drums, drum arrays, etc., the engineers at IBM's San Jose California laboratory invented the hard disk drive. The disk drive created a new level in the computer data hierarchy, then termed Random Access Storage but today known as secondary storage, less expensive and slower than main memory (then typically drums and later core memory) but faster and more expensive than tape drives. The commercial usage of hard disk drives (HDD) began in 1957, with the shipment of a production IBM 305 RAMAC system including IBM Model 350 disk storage. US Patent 3,503,060 issued March 24, 1970, and arising from the IBM RAMAC program is generally considered to be the fundamental patent for disk drives. Each generation of disk drives replaced larger, more sensitive and more cumbersome devices. The earliest drives were usable only in the protected environment of a data center. Later generations progressively reached factories, offices and homes, eventually becoming ubiquitous. Disk media diameter was initially 24 inches, but over time it has been reduced to today's 3.5-inch and 2.5-inch standard sizes. Drives with the larger 24-inch- and 14-inch-diameter media were typically mounted in standalone boxes (resembling washing machines) or large equipment rack enclosures. Individual drives often required high-current AC power due to the large motors required to spin the large disks. Drives with smaller media generally conformed to de facto standard form factors. The capacity of hard drives has grown exponentially over time. When hard drives became available for personal computers, they offered 5-megabyte capacity. During the mid-1990s the typical hard disk drive for a PC had a capacity of about 1 gigabyte. As of August 2020, desktop hard disk drives typically had a capacity of 1 to 8 terabytes, with the largest-capacity drives reaching 20 terabytes (single-disk drives, "dual" drives are available up to 24 TB). Smaller, laptop internal 2.5-inch drives, are available up to 5 TB. Unit production peaked in 2010 at about 650 million units and has been in a slow decline since then. (en)
- ハードディスクドライブの歴史（ハードディスクドライブのれきし）では、ハードディスクドライブ (HDD) の歴史を記述する。 (ja)
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| rdfs:comment
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- ハードディスクドライブの歴史（ハードディスクドライブのれきし）では、ハードディスクドライブ (HDD) の歴史を記述する。 (ja)
- In 1953, IBM recognized the immediate application for what it termed a "Random Access File" having high capacity and rapid random access at a relatively low cost. After considering technologies such as wire matrices, rod arrays, drums, drum arrays, etc., the engineers at IBM's San Jose California laboratory invented the hard disk drive. The disk drive created a new level in the computer data hierarchy, then termed Random Access Storage but today known as secondary storage, less expensive and slower than main memory (then typically drums and later core memory) but faster and more expensive than tape drives. (en)
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