The earliest “form factor” hard disk drives inherited their dimensions from floppy-disk drives (FDDs), so that either could be mounted in chassis slots, and thus the HDD form factors became colloquially named after the corresponding FDD types. "Form factor" compatibility continued after the 3½ in size even though floppy disk drives with new smaller dimensions ceased to be offered.

• "8 inch" drive: (9.5 in x 4.624 in x 14.25 in = 241.3 mm x 117.5 mm x 362 mm)
  In 1979, Shugart Associates' SA1000 was the first form factor compatible HDD, having the same dimensions and a compatible interface to the 8" FDD. Both "full height" and "half height" (2.313 in) versions were available.

• "5¼ inch" drive: (5.75 in x 1.63 in x 8 in = 146.1 mm x 41.4 mm x 203 mm)
  This smaller form factor, first used in an HDD by Seagate in 1980, was the same size as full height 5¼-inch diameter FDD, i.e., 3.25 inches high. This is twice as high as commonly used today; i.e., 1.63 in = 41.4 mm (“half height”). Most desktop models of drives for optical 120 mm disks (DVD, CD) use the half height 5¼" dimension, but it fell out of fashion for HDDs. The Quantum “Bigfoot” HDD was the last to use it in the late 1990s, with “low-profile” (~25 mm) and “ultra-low-profile” (~20 mm) high versions.

• "3½ inch" drive: (4 in x 1 in x 5.75 in = 101.6 mm x 25.4 mm x 146 mm)
  This smaller form factor, first used in an HDD by Rodime in 1984, was the same size as the "half height" 3½ FDD, i.e., 1.63 inches high. Today has been largely superseded by 1-inch high “slimline” or “low-profile” versions of this form factor which is used by most desktop HDDs.

• "2½ inch" drive: (2.75 in x 0.374 in x 3.945 in = 69.85 mm x 9.5 mm x 100 mm)
  This smaller form factor was introduced by PrairieTek in 1988; there is no corresponding FDD. It is widely used today for hard-disk drives in mobile devices (laptops, music players, etc.). Today, the dominant height of this form factor is 9.5 mm, but there were also 19 mm, 17 mm, and 12.5 mm high variants in use.

• "1.8 inch" drive: (54 mm × 8 mm × 71 mm)
  This form factor, originally introduced by Integral Peripherals in 1993, has evolved into the ATA-7 LIF with dimensions as stated. It is increasingly used in digital audio players and subnotebooks. An original variant exists for 2–5 GB sized HDDs that fit directly into a PC card expansion slot.

• "1 inch" drive: (42.8 mm × 5 mm × 36.4 mm)
  This form factor was introduced in 1999 as IBM's Microdrive to fit inside a CF Type II slot.

• "0.85 inch" drive: (24 mm × 5 mm × 32 mm)
  Toshiba announced this form factor in January 2004[24] for use in mobile phones and similar applications, including SD/MMC slot compatible HDDs optimized for video storage on 4G handsets. Toshiba currently sells a 4 GB (MK4001MTD) and 8 GB (MK8003MTD) version[3] and holds the Guinness World Record for the smallest harddisk drive.[25]

Major manufacturers discontinued the development of new products for the 1-inch and 0.85-inch form factors in 2007, due to falling prices of flash memory.[26]
The inch-based nickname of all these form factors usually do not indicate any actual product dimension (which are for more recent form factors specified in millimeters), but just roughly indicate a size relative to disk diameters, in the interest of historic continuity.

Other characteristics

Capacity of a hard disk drive is usually quoted in gigabytes. Older HDDs quoted their smaller capacities in megabytes.
The data transfer rate at the inner zone ranges from 44.2 MB/s to 74.5 MB/s, while the transfer rate at the outer zone ranges from 74.0 MB/s to 111.4 MB/s. An HDD's random access time ranges from 5 ms to 15 ms.


Contents:

• 1 Main page of hard drive
• 2 Technology
• 3 Capacity and access speed
• 4 Access and interfaces
• 5 Integrity
• 6 Manufacturers