HDDs are a type of non-volatile storage, retaining stored data even when powered off. Data is accessed in a random-access manner, meaning that individual blocks of data can be stored and retrieved in any order. The platters are paired with magnetic heads, usually arranged on a moving actuator arm, which read and write data to the platter surfaces. A hard disk drive ( HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage and one or more rigid rapidly rotating platters coated with magnetic material. This hard drive is designed to quickly and easily store and transfer media files such as digital photos, music, video, and other. The HP External Portable USB 3.0 Hard Drive is a large capacity USB 3.0 external hard drive that can connect and disconnect easily from a USB 3.0 or USB 2.0 connector on the front, back, or side of most computers.
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More than 224 companies have produced HDDs historically, though after extensive industry consolidation most units are manufactured by Seagate, Toshiba, and Western Digital. HDDs maintained this position into the modern era of servers and personal computers, though personal computing devices produced in large volume, like cell phones and tablets, rely on flash memory storage devices. Introduced by IBM in 1956, HDDs were the dominant secondary storage device for general-purpose computers beginning in the early 1960s. Toshiba 1TB External USB 3.0 Portable. Features: Big Capacity in a Small Package With up to 4TB of storage in a slim and stylish portable hard drive, the Canvio Advance allows for you to store thousands of pictures, videos, music, or a variety of large files on a small 2.5' portable drive.Toshiba External Portable Hard Drive 500GB(HDTC605XK3A1) Black Color Used. Enjoy a sleek design in a compact casing with up to 4TB(1) of storage.Toshiba Canvio Advance Hdtc940xr3ca 4 Tb Portable Hard Drive - 2.5' External - Red.
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Cash on Delivery and Free Home Delivery at Flipkart.com.The primary characteristics of an HDD are its capacity and performance. Buy 1TB, 2TB Toshiba External Hard Disk - Check Portable Hard Drives Review and Price in India. Cost per bit for SSDs is falling, and the price premium over HDDs has narrowed.
The 350 had a single arm with two read/write heads, one facing up and the other down, that moved both horizontally between a pair of adjacent platters and vertically from one pair of platters to a second set. It was approximately the size of two medium-sized refrigerators and stored five million six-bit characters (3.75 megabytes) on a stack of 52 disks (100 surfaces used). HDDs are connected to systems by standard interface cables such as PATA (Parallel ATA), SATA (Serial ATA), USB or SAS ( Serial Attached SCSI) cables.Video of modern HDD operation (cover removed) Improvement of HDD characteristics over timeUS$9,200 per megabyte (1961 US$83,107 in 2021) US$0.024 per gigabyte by 2020 1.3 terabits per square inch in 2015 The first production IBM hard disk drive, the 350 disk storage, shipped in 1957 as a component of the IBM 305 RAMAC system. Performance is specified by the time required to move the heads to a track or cylinder (average access time) adding the time it takes for the desired sector to move under the head (average latency, which is a function of the physical rotational speed in revolutions per minute), and finally the speed at which the data is transmitted (data rate).The two most common form factors for modern HDDs are 3.5- inch, for desktop computers, and 2.5-inch, primarily for laptops. Also there is confusion regarding storage capacity, since capacities are stated in decimal gigabytes (powers of 1000) by HDD manufacturers, whereas the most commonly used operating systems report capacities in powers of 1024, which results in a smaller number than advertised. Typically, some of an HDD's capacity is unavailable to the user because it is used by the file system and the computer operating system, and possibly inbuilt redundancy for error correction and recovery.
The 1301 cabinet was about the size of three home refrigerators placed side by side, storing the equivalent of about 21 million eight-bit bytes per module. Motion of the head array depended upon a binary adder system of hydraulic actuators which assured repeatable positioning. Cylinder-mode read/write operations were supported, and the heads flew about 250 micro-inches (about 6 µm) above the platter surface. While the earlier IBM disk drives used only two read/write heads per arm, the 1301 used an array of 48 heads (comb), each array moving horizontally as a single unit, one head per surface used. The 1301 consisted of one (for Model 1) or two (for model 2) modules, each containing 25 platters, each platter about 1⁄ 8-inch (3.2 mm) thick and 24 inches (610 mm) in diameter.
Non-removable HDDs were called "fixed disk" drives.In 1963 IBM introduced the 1302, with twice the track capacity and twice as many tracks per cylinder as the 1301. Later models of removable pack drives, from IBM and others, became the norm in most computer installations and reached capacities of 300 megabytes by the early 1980s. Users could buy additional packs and interchange them as needed, much like reels of magnetic tape.
Instead, the first models of "Winchester technology" drives featured a removable disk module, which included both the disk pack and the head assembly, leaving the actuator motor in the drive upon removal. This greatly reduced the cost of the head actuator mechanism, but precluded removing just the disks from the drive as was done with the disk packs of the day. Instead, the heads were allowed to "land" on a special area of the disk surface upon spin-down, "taking off" again when the disk was later powered on. Its primary distinguishing feature was that the disk heads were not withdrawn completely from the stack of disk platters when the drive was powered down. In 1973, IBM introduced a new type of HDD code-named " Winchester". Known as fixed-head or head-per-track disk drives, they were very expensive and are no longer in production.
The subsystem was not sold under the drive manufacturer's name but under the subsystem manufacturer's name such as Corvus Systems and Tallgrass Technologies, or under the PC system manufacturer's name such as the Apple ProFile. Powerful rare earth magnet materials became affordable during this period, and were complementary to the swing arm actuator design to make possible the compact form factors of modern HDDs.As the 1980s began, HDDs were a rare and very expensive additional feature in PCs, but by the late 1980s their cost had been reduced to the point where they were standard on all but the cheapest computers.Most HDDs in the early 1980s were sold to PC end users as an external, add-on subsystem. The latter were primarily intended for the then fledgling personal computer (PC) market.Over time, as recording densities were greatly increased, further reductions in disk diameter to 3.5" and 2.5" were found to be optimum. Other eight inch drives followed, then 5 + 1⁄ 4 in (130 mm) drives, sized to replace the contemporary floppy disk drives. In 1978 IBM introduced a swing arm drive, the IBM 0680 (Piccolo), with eight inch platters, exploring the possibility that smaller platters might offer advantages. The simple design of the IBM GV (Gulliver) drive, invented at IBM's UK Hursley Labs, became IBM's most licensed electro-mechanical invention of all time, the actuator and filtration system being adopted in the 1980s eventually for all HDDs, and still universal nearly 40 years and 10 Billion arms later.Like the first removable pack drive, the first "Winchester" drives used platters 14 inches (360 mm) in diameter.
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