In computing, mass storage refers to the storage of large amounts of data in a persisting and machine-readable fashion. In general the term is uses as large in relation to contemporaneous disk drives, but it has been used large in relation to RAM as for example with floppy disks.
Devices and/or systems that have been described as mass storage include tape libraries, RAID systems, and a variety of computer drives such as hard disk drives, magnetic tape drives, magneto-optical disc drives, optical disc drives, memory cards, and solid-state drives. It also includes experimental forms like holographic memory. Mass storage includes devices with removable and non-removable media. It does not include random access memory (RAM).
There are two broad classes of mass storage: local data in devices such as smartphones or computers, and enterprise servers and data centers for the cloud. For local storage, SSDs are on the way to replacing HDDs. Considering the mobile segment from phones to notebooks, the majority of systems today is based on NAND Flash. As for Enterprise and data centers, storage tiers have established using a mix of SSD and HDD. 
The notion of "large" amounts of data is of course highly dependent on the time frame and the market segment, as storage device capacity has increased by many orders of magnitude since the beginnings of computer technology in the late 1940s and continues to grow; however, in any time frame, common mass storage devices have tended to be much larger and at the same time much slower than common realizations of contemporaneous primary storage technology.
Papers at the 1966 Fall Joint Computer Conference (FJCC) used the term mass storage for devices substantially larger than contemporaneous hard disk drives. Similarly, a 1972 analysis identified mass storage systems from Ampex (Terabit Memory) using video tape, Precision Industries (Unicon 690-212) using lasers and International Video (IVC-1000) using video tape and states "In the literature, the most common definition of mass storage capacity is a trillion bits.". The first IEEE conference on mass storage was held in 1974 and at that time identified mass storage as "capacity on the order of 1012 bits" (1 gigabyte). In the mid-1970s IBM used the term to in the name of the IBM 3850 Mass Storage System, which provided virtual disks backed up by Helical scan magnetic tape cartridges, slower than disk drives but with a capacity larger than was affordable with disks. The term mass storage was used in the PC marketplace for devices, such as floppy disk drives, far smaller than devices that were not[a] considered mass storage in the mainframe marketplace.
Mass storage devices are characterized by:
- Sustainable transfer speed
- Seek time
Magnetic disks are the predominant storage media in personal computers. Optical discs, however, are almost exclusively used in the large-scale distribution of retail software, music and movies because of the cost and manufacturing efficiency of the molding process used to produce DVD and compact discs and the nearly-universal presence of reader drives in personal computers and consumer appliances. Flash memory (in particular, NAND flash) has an established and growing niche as a replacement for magnetic hard disks in high performance enterprise computing installations due to its robustness stemming from its lack of moving parts, and its inherently much lower latency when compared to conventional magnetic hard drive solutions. Flash memory has also long been popular as removable storage such as USB sticks, where it de facto makes up the market. This is because it scales better cost-wise in lower capacity ranges, as well as its durability. It has also made its way onto laptops in the form of SSDs, sharing similar reasons with enterprise computing: Namely, markedly high degrees of resistance to physical impact, which is again, due to the lack of moving parts, as well as a performance increase over conventional magnetic hard disks and markedly reduced weight and power consumption. Flash has also made its way onto cell phones.
Mass storage devices used in desktop and most server computers typically have their data organized in a file system. The choice of file system is often important in maximizing the performance of the device: general purpose file systems (such as NTFS and HFS, for example) tend to do poorly on slow-seeking optical storage such as compact discs.
Some relational databases can also be deployed on mass storage devices without an intermediate file system or storage manager. Oracle and MySQL, for example, can store table data directly on raw block devices.
On removable media, archive formats (such as tar archives on magnetic tape, which pack file data end-to-end) are sometimes used instead of file systems because they are more portable and simpler to stream.
On embedded computers, it is common to memory map the contents of a mass storage device (usually ROM or flash memory) so that its contents can be traversed as in-memory data structures or executed directly by programs.
- Data storage for general overview of storage methods
- E.g., the obsolete 1956 IBM 350 stored 5 million six-bit characters, larger than contemporary 1.44 and 2.88 MB floppies.
- "Definition of: mass storage". PC Magazine. Ziff Davis. Archived from the original on 2016-07-05. Retrieved 2019-10-10.
- Sterling, Thomas; Anderson, Matthew; Brodowicz, Maciej (2018). "17 – Mass storage". High performance computing. Morgan Kaufmann (Elsevier). ISBN 978-0-12-420158-3.
- https://www.hyperstone.com/en/NAND-Flash-is-displacing-hard-disk-drives-1249,12728.html, NAND Flash is displacing Hard Disk Drives, Retrieved 29. May 2018
- 1966FJCC, pp. 711-742, TECHNOLOGIES AND SYSTEMS FOR ULTRA-HIGH CAPACITY STORAGE. sfn error: no target: CITEREF1966FJCC (help)
- 1966FJCC, pp. 711-716, UNICON Computer Mass Memory System, C.H.BECKER. sfn error: no target: CITEREF1966FJCC (help)
- 1966FJCC, pp. 735-742, A Photo-Digital Mass Storage System, J. D. KUEHLER, H. R. KERBY. sfn error: no target: CITEREF1966FJCC (help)
1966 Fall Joint Computer Conference. AFIPS Conference Proceedings. Vol. 29. Spartan Books. ISBN 978-1-4503-7893-2. 1966FJCC.
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- Norman F. Schneidewind; Gordon H. Syms; Thomas L. Grainger; Robert J. Carden (July 1972). A SURVEY AND ANALYSIS OF HIGH DENSITY MASS STORAGE DEVICES AND SYSTEMS (Report). US Navy Postgraduate School, Monterey CA. CiteSeerX 10.1.1.859.1517. NPS-55SS72071A. Retrieved December 3, 2020.
- NPS-55SS72071A, p. 6, A. Definition and Uses of Mass Storage.
- The 35th conference was held in 2019.
- Bacon, G. C. (October 1974). "Mass Storage Workshop Report". Computer. IEEE. 7 (10): 64–65. doi:10.1109/MC.1974.6323336. S2CID 29301138. Retrieved December 3, 2020.
- Introduction to the IBM 3850 Mass Storage System (MSS) (PDF) (Second ed.). IBM. November 1974. GA32-0028-1.
- Taylor, Jim. "DVD FAQ". Archived from the original on 2009-08-22. Retrieved 2007-07-08.
In 2003, six years after introduction, there were over 250 million DVD playback devices worldwide, counting DVD players, DVD PCs, and DVD game consoles.
- Gonsalves, Antone (23 May 2007). "Micron predicts flash memory will replace disk drives". EETimes..
- Heingartner, Douglas (2005-02-17). "Flash Drives: Always on the Go, Without Moving Parts". New York Times. Retrieved 2008-02-24..
- Patterson, Dave (June 2003). "A Conversation With Jim Gray". ACM Queue. 1 (4). Archived from the original (– Scholar search) on April 21, 2005.. (A discussion of recent trends in mass storage.)