and magnetic recording
are terms from engineering
referring to the storage of data
on a magnetized
medium. Magnetic storage uses different patterns of magnetization
in a magnetizable material to store data and is a form of non-volatile memory
. The information is accessed using one or more read/write heads
. As of 2007, magnetic storage media, primarily hard disks
, are widely used to store computer data
as well as audio
signals. In the field of computing, the term magnetic storage
is preferred and in the field of audio and video production, the term magnetic recording
is more commonly used. The distinction is less technical and more a matter of preference.
Magnetic storage was first suggested by Oberlin Smith
in 1888. The first working magnetic recorder was invented by Valdemar Poulsen
in 1898. Poulsen's device recorded a signal
on a wire wrapped around a drum. In 1928, Fritz Pfleumer
developed the first magnetic tape recorder
. Early magnetic storage devices were designed to record analog
audio signals. Modern magnetic storage devices are designed for recording digital
In early computers, magnetic storage was also used for primary storage in a form of magnetic drum, or core memory, core rope memory, thin film memory, twistor memory or bubble memory. Unlike modern computers, magnetic tape was also often used for secondary storage.
Magnetic storage media can be classified as either sequential access memory
or random access memory
although in some cases the distinction is not perfectly clear. In the case of magnetic wire, the read/write head only covers a very small part of the recording surface at any given time. Accessing different parts of the wire involves winding the wire forward or backward until the point of interest is found. The time to access this point depends on how far away it is from the starting point. The case of ferrite-core memory is the opposite. Every core location is immediately accessible at any given time.
Hard disks and modern linear serpentine tape drives do not precisely fit into either category. Both have many parallel tracks across the width of the media and the read/write heads take time to switch between tracks and to scan within tracks. Different spots on the storage media take different amounts of time to access. For a hard disk this time is typically less than 10 ms, but tapes might take as much as 100 s.
As of 2007, common uses of magnetic storage media are for computer data mass storage on hard disks and the recording of analog audio and video works on analog tape
. Since much of audio and video production is moving to digital systems, the usage of hard disks is expected to increase at the expense of analog tape. Digital tape
and tape libraries
are popular for the high capacity data storage of archives and backups. Floppy disks
see some marginal usage, particularly in dealing with older computer systems and software. Magnetic storage is also widely used in some specific applications, such as bank checks (MICR
) and payment cards (mag stripes
A new type of magnetic storage, called MRAM
, is being produced that stores data
in magnetic bits based on the GMR
effect. Its advantage is non-volatility, low power usage, and good shock robustness. However, with storage density and capacity orders of magnitude smaller than e.g. an HDD
, MRAM is a niche application for situations where small amounts of storage with a need for very frequent updates are required, which flash memory
could not support.