Flying height
The flying height or floating height or head gap is the distance between the disk read/write head on a hard disk drive and the platter. The first commercial hard-disk drive, the IBM 305 RAMAC, used forced air to maintain a 0.002-inch (51-micron) spacing between the head and disk. The IBM 1301, introduced in 1961, was the first disk drive in which the head was attached to a "hydrodynamic air bearing slider," which generates its own cushion of pressurized air, allowing the slider and head to fly much closer, 250 microinches (6.35 micrometers) above the disk surface.[1]
In 2011, the flying height in modern drives was a few nanometers.[2] Thus, the head can collide with even an obstruction as thin as a fingerprint or a particle of smoke. Despite the dangers of hard drive failure from such foreign objects, hard drives generally allow for ventilation (albeit through a filter) so that the air pressure within the drive can equalize with the air pressure outside.[3] Because disk drives depend on the head floating on a cushion of air, they are not designed to operate in a vacuum. Regulation of flying height will become even more important in future high-capacity drives.[4]
However, hermetically sealed enclosures are beginning to be adopted for hard drives filled with helium gas, with first the products launched in December 2015,[5] starting with capacities of 10 TB.[5][6]
See also
References
- ^ "Timeline of IBM San Jose Research Laboratory" (PDF).
- ^ "Dynamic Flying Height Adjustment in Hard Disk Drives Through Feedforward Control" (PDF). IEEE Transactions on Magnetics. 47 (7): 1823–1829. July 2011.
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ignored (help) - ^ Charles M. Kozierok. "Hard Disk Read/Write Head Operation". The PC Guide.
- ^ "Drive level measurement of flying height modulation and control of slider disk contact". Tribology Letters. 24 (2): 159–162. 27 November 2006. doi:10.1007/s11249-006-9153-1.
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ignored (help) - ^ a b Lucas Mearian (2 December 2015). "WD ships world's first 10TB helium-filled hard drive". Computerworld.
- ^ Gabe Carey (14 January 2016). "Seagate is finally joining HGST in its helium-filled hard drive efforts". Digital Trends.