Form Factors
| Form factor | Status | Width (mm) | Height (mm) | Largest capacity | Platters (max) | Capacity Per platter (GB) |
|---|---|---|---|---|---|---|
| 3.5" | Current | 102 | 19 or 25.4 | 4 TB (2011) | 5 | 1000 |
| 2.5" | Current | 69.9 | 5, 7, 9.5, 12.5, or 15 | 2 TB (2012) | 4 | 500 |
| 1.8" | Current | 54 | 5 or 8 | 320 GB (2009) | 2 | 160 |
| 5.25" FH | Obsolete | 146 | 47 GB (1998) | 14 | 3.36 | |
| 5.25" HH | Obsolete | 146 | 19.3 GB (1998) | 4 | 4.83 | |
| 1.3" | Obsolete | 43 | 40 GB (2007) | 1 | 40 | |
| 1" (CFII/ZIF/IDE-Flex) | Obsolete | 42 | 20 GB (2006) | 1 | 20 | |
| 0.85" | Obsolete | 24 | 8 GB (2004) | 1 | 8 |
Mainframe and minicomputer hard disks were of widely varying dimensions, typically in free standing cabinets the size of washing machines or designed to fit a 19" rack. In 1962, IBM introduced its model 1311 disk, which used 14 inch (nominal size) platters. This became a standard size for mainframe and minicomputer drives for many years, but such large platters were never used with microprocessor-based systems.
With increasing sales of microcomputers having built in floppy-disk drives (FDDs), HDDs that would fit to the FDD mountings became desirable. Thus HDD Form factors, initially followed those of 8-inch, 5.25-inch, and 3.5-inch floppy disk drives. Because there were no smaller floppy disk drives, smaller HDD form factors developed from product offerings or industry standards.
- 8 inch
- 9.5 in × 4.624 in × 14.25 in (241.3 mm × 117.5 mm × 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.
- 5.25 inch
- 5.75 in × 3.25 in × 8 in (146.1 mm × 82.55 mm × 203 mm). This smaller form factor, first used in an HDD by Seagate in 1980, was the same size as full-height 51⁄4-inch-diameter (130 mm) FDD, 3.25-inches high. This is twice as high as "half height"; i.e., 1.63 in (41.4 mm). 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.
- 3.5 inch
- 4 in × 1 in × 5.75 in (101.6 mm × 25.4 mm × 146 mm) = 376.77344 cm³. This smaller form factor is similar to that used in an HDD by Rodime in 1983, which was the same size as the "half height" 3½" FDD, i.e., 1.63 inches high. Today, the 1-inch high ("slimline" or "low-profile") version of this form factor is the most popular form used in most desktops.
- 2.5 inch
- 2.75 in × 0.275–0.59 in × 3.945 in (69.85 mm × 7–15 mm × 100 mm) = 48.895–104.775 cm3. This smaller form factor was introduced by PrairieTek in 1988; there is no corresponding FDD. It came to be widely used for HDDs in mobile devices (laptops, music players, etc.) and for solid-state drives, by 2008 replacing some 3.5 inch enterprise-class drives. It is also used in the PlayStation 3 and Xbox 360 video game consoles. Drives 9.5 mm high became an unofficial standard for all except the largest-capacity laptop drives (usually having two platters inside); 12.5 mm-high drives, typically with three platters, are used for maximum capacity, but will not fit most laptop computers. Enterprise-class drives can have a height up to 15 mm. Seagate released a 7mm drive aimed at entry level laptops and high end netbooks in December 2009.
- 1.8 inch
- 54 mm × 8 mm × 71 mm = 30.672 cm³. This form factor, originally introduced by Integral Peripherals in 1993, evolved into the ATA-7 LIF with dimensions as stated. For a time it was increasingly used in digital audio players and subnotebooks, but its popularity decreased to the point where this form factor is increasingly rare and only a small percentage of the overall market.
- 1 inch
- 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. Samsung calls the same form factor "1.3 inch" drive in its product literature.
- 0.85 inch
- 24 mm × 5 mm × 32 mm. Toshiba announced this form factor in January 2004 for use in mobile phones and similar applications, including SD/MMC slot compatible HDDs optimized for video storage on 4G handsets. Toshiba manufactured a 4 GB (MK4001MTD) and an 8 GB (MK8003MTD) version and holds the Guinness World Record for the smallest HDD.
As of 2012, 3.5-inch and 2.5-inch hard disks were the most popular sizes.
By 2009 all manufacturers had discontinued the development of new products for the 1.3-inch, 1-inch and 0.85-inch form factors due to falling prices of flash memory, which has no moving parts.
While these sizes are customarily described by an approximately correct figure in inches, actual sizes have long been specified in millimeters.
Read more about this topic: Hard Disk Drive
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