Magnetic storage is a data storage technology that uses magnetic polarization to store and retrieve digital information. It operates based on the principle that information can be represented and recorded on magnetic media by the direction and strength of the magnetization on distinct regions of the material.
The history of magnetic storage goes back to the late 1930s when researchers at the Carnegie Institution in Washington D.C. accidentally discovered a new alloy called Perminvar that showed evidence of magnetic anisotropy (directional dependence). This sparked the idea to use the orientation of magnetic domains on the surface of media to encode information. Early prototypes of magnetic storage devices like magnetic drums and core memory were built in the 1940s and 1950s (https://www.researchgate.net/publication/328870642_A_brief_history_of_magnetic_storage).
In magnetic storage devices, binary data is stored by magnetizing tiny regions on the surface of magnetic media like tapes and disks. These magnetized regions, often called magnetic domains, are used to represent 1s and 0s. Data can be read back by detecting the magnetization of each domain. The data is protected as long as the magnetic surface is kept away from demagnetizing influences.
Hard Disk Drives
Hard disk drives (HDD) are one of the most common forms of magnetic data storage. They consist of one or more rigid platters coated with a ferromagnetic material that act as the medium for storing data. Data is written to and read from the platter using a read/write head that floats just above the surface of the platter on an air bearing.
To write data, the read/write head receives an electrical signal that polarizes the region of the platter directly beneath it, encoding 1s and 0s magnetically. The data is organized in concentric tracks across the surface of the platter. To increase storage capacity, platters are stacked on top of each other and read/write heads access each surface.
To read the stored data, the read/write head detects the magnetic polarization of the platter as it passes underneath and generates an electrical signal based on the magnetic flux changes. The signal is then decoded into the original 1s and 0s that make up the data. HDDs use moving parts like actuator arms to accurately position read/write heads over specific tracks on the platter to access stored data.
Floppy Disks
Floppy disks were one of the earliest forms of portable magnetic data storage. The first floppy disks were developed in the late 1960s and were 8 inches in diameter. They were able to hold just 80 kilobytes of data. The name “floppy disk” comes from the fact that the disk itself inside its protective casing is flexible, or floppy.
In the 1970s, smaller 5.25 inch floppy disks were introduced that could hold up to 360 kilobytes of data. The most common and widely used floppy disk format was the 3.5 inch disk, introduced in the 1980s by Sony. These disks held up to 1.44 megabytes of data and became ubiquitous for personal computer data storage and transfer until larger capacity USB flash drives became more common in the 2000s.[1]
Data is stored on floppy disks magnetically. The disk contains a thin magnetic coating made up of ferrous oxide particles. As the disk spins, a read/write head hovers over the disk to detect or change the magnetization of the particles to write or read binary data. The flexible nature of the disk allows the read/write head to maintain close contact with the media.
While floppy disks have been made largely obsolete by other storage technologies, they played an important historical role in the adoption of personal computers by allowing content and programs to be easily shared between users.[2]
Sources:
- [1] https://heirloom.cloud/post/the-floppy-disk-a-brief-history
- [2] https://www.quora.com/What-is-the-memory-capacity-of-a-floppy-disk
Magnetic Tape
Magnetic tape has been used for data storage since the 1950s. It was the main form of offline, external storage for computers throughout the 1960s until the 1980s when hard disk drives became more affordable and had greater storage capacities. Magnetic tape is primarily used today for long-term archival storage.
Magnetic tape uses linear data recording where data is stored across the width of the tape in parallel tracks. This differs from helical scan recording used in video tape recording where data is recorded diagonally in a helix pattern across the width of the tape. Linear recording allows for much greater data densities which is critical for data storage applications (https://en.wikipedia.org/wiki/Magnetic-tape_data_storage).
The data density or storage capacity of magnetic tapes has increased dramatically over the decades through advances in the magnetic layer quality and tape transport mechanisms. In 2014, Fujifilm and IBM developed a prototype tape cartridge that could store 123 billion bits per square inch, for a total of 220 terabytes of uncompressed data on a single cartridge (https://spectrum.ieee.org/why-the-future-of-data-storage-is-still-magnetic-tape). In December 2020, Fujifilm and IBM announced a new prototype that achieved a record 317 gigabits per square inch density (https://newatlas.com/computers/ibm-fujifilm-magnetic-tape-data-storage/).
Magneto-Optical Drives
Magneto-optical drives use optical-laser technology and magnetic fields to store data on special media called MO disks (Magneto-Optical disks). Data is written on the MO disk by heating one of the magnetic layers in the disk with a laser. This causes the heated area to be magnetized according to the direction of the external magnetic field generated by the drive’s magnetic heads. The MO disk has multiple layers of magnetic material that can be magnetized in different directions to represent 0s and 1s for digital data storage.
To read data, a low-power polarized laser beam is directed onto the MO disk. Due to something called the Kerr Effect, the polarization of the reflected light will change based on the magnetic orientation of the media. These changes in the reflected light are then decoded into 1s and 0s to read the stored data.
Compared to traditional magnetic storage like hard drives, magneto-optical drives offer advantages like higher storage capacities, longer lifespan, and better portability due to the durability of MO disks. However, MO drives have slower data transfer rates compared to HDDs and are also susceptible to data corruption from extreme heat or magnetic fields. Overall, magneto-optical storage offers a unique combination of portability, capacity, and reliability compared to other magnetic storage technologies.
Early Magnetic Storage
The first magnetic storage devices emerged in the late 19th and early 20th centuries. Some key early developments include:
Wire recording, invented in 1898 by Danish engineer Valdemar Poulsen, was the first device to magnetically record sound. It used a magnetizable steel wire to capture audio signals. Magnetic storage
Magnetic drum memory, developed in 1932 by Austrian engineer Gustav Tauschek, was an early form of magnetic disk storage. Drums were metal cylinders coated in magnetic iron oxide material that stored data in circular tracks. A Brief History of Data Storage
Magnetic core memory, introduced in the 1940s, used tiny magnetic rings called cores to store bits. Arranged in grids, the magnetization of each core represented 1 or 0. Core memory was the predominant form of RAM through the 1960s. Magnetic-core memory
These early devices pioneered magnetic techniques for recording and storing data electronically. Though limited in capacity, they marked major breakthroughs in memory technology at the time.
Current Applications
While magnetic storage technology like floppy disks and tape drives were once used for personal computing and data storage, their usage has declined dramatically with the rise of optical and solid state storage devices like CDs, DVDs, USB drives, and SSDs. However, magnetic tape is still commonly used for long-term data backup and archiving purposes (Wikipedia, 2022).
Magnetic tape offers advantages like longevity, capacity, and low cost compared to other backup media. Tape libraries are used by many corporations and organizations to store backup copies of critical data in case of a disaster. For example, the Sunway TaihuLight supercomputer in China uses over 100 petabytes of magnetic tape for storage and backup (Quora, 2017).
In addition, magnetic tape is still used for some specialized applications like data warehousing, where large volumes of records need to be stored and accessed sequentially. Overall, while magnetic storage use has declined in end user devices, it remains an important technology for large-scale and archival data storage applications.
Advantages of Magnetic Storage
One of the main advantages of magnetic storage is its low cost per megabyte compared to other storage mediums. Magnetic tape and hard disk drives can store large amounts of data very cheaply. For example, a 10 terabyte hard drive may cost around $200, which is only $0.02 per gigabyte (University). This makes it very affordable to store large amounts of data with magnetic storage.
Another advantage is the reusability of magnetic tape and disks. After data is deleted or overwritten, the storage medium can be reused repeatedly. Hard disk drives are rated for hundreds of thousands of hours of use, while magnetic tapes can be erased and rewritten many times (Shredall). This makes magnetic storage a good choice when reuse is important.
Magnetic storage also provides high storage density in a small form factor. For instance, modern hard drives can store terabytes of data in a 3.5″ drive bay. And advances in technology continue to increase the data density of magnetic disk and tape. This allows large storage capacities without taking up much space (Salvagedata).
Overall, the low cost, reusability, and high storage density make magnetic storage advantageous for many applications where large amounts of data need to be stored affordably.
Disadvantages of Magnetic Storage
Magnetic storage has some notable drawbacks compared to newer storage technologies like solid state drives. Some key disadvantages include:
Access speed – Retrieving data from magnetic storage is relatively slow due to the mechanical nature of the spinning disks and moving heads. Access times are typically in the millisecond range.
Data corruption – Magnetic storage is susceptible to data corruption and loss from external magnetic fields or electrostatic discharge (ESD) events. As noted by 3DFortify, “One of the key drawbacks of magnetic data storage is that it is very susceptible to ESD events which can alter or corrupt any data that is stored.”1
Limited lifespan – The mechanical components of magnetic storage devices eventually wear out and fail after repeated use. HDDs and tapes have a typical lifespan of 3-5 years.
The Future of Magnetic Storage
Magnetic storage technologies continue to evolve to meet growing data storage demands. Some innovations on the horizon include:
Heat-assisted magnetic recording (HAMR) uses laser thermal assistance to temporarily heat the recording medium and make it easier to magnetize areas of greater density and stability. This allows for higher storage densities, as small as 1 terabit per square inch. Research indicates HAMR has potential for areal densities up to 10 Tb/in2 (Thompson, 2000).
Bit patterned media creates discrete magnetic islands on the platter surface, each capable of representing a single bit. This increases Signal-to-Noise Ratio and enables greater storage densities, perhaps up to 10 Tb/in2. However, manufacturing bit patterned media remains challenging (Thompson, 2000).
Shingled magnetic recording (SMR) partially overlaps data tracks like shingles on a roof to increase platter densities. However, this makes the tracks more difficult to update and requires novel reading/writing approaches. SMR drives are estimated to reach capacities of 40 TB by 2020 (Thompson, 2000).
While facing physical limits, magnetic storage technologies continue to evolve and extend capacities. Heat-assisted recording, patterned media, shingled recording and other innovations aim to prolong the reign of magnetic storage.