Incomputing,mass storage refers to thestorage of large amounts ofdata in apersisting andmachine-readable fashion. In general, the termmass inmass storage is used to meanlarge in relation to contemporaneous hard disk drives, but it has also been used to meanlarge relative to the size ofprimary memory as for example withfloppy disks onpersonal computers.
Devices and/or systems that have been described as mass storage includetape libraries,RAID systems, and a variety ofcomputer drives such ashard disk drives (HDDs),magnetic tape drives,magneto-optical disc drives,optical disc drives,memory cards, andsolid-state drives (SSDs). It also includes experimental forms likeholographic memory. Mass storage includes devices withremovable and non-removable media.[1][2] It does not includerandom access memory (RAM).
There are two broad classes of mass storage: local data in devices such assmartphones orcomputers, 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 onNAND Flash. As for Enterprise anddata centers, storage tiers have established using a mix ofSSD andHDD.[3]
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 contemporaneousprimary storage technology.
Papers[4][5][6] at the 1966Fall Joint Computer Conference[7] (FJCC) used the termmass storage for devices substantially larger than contemporaneous hard disk drives. Similarly, a 1972 analysis identified mass storage systems fromAmpex (Terabit Memory) using video tape, Precision Industries (Unicon 690-212) using lasers and International Video (IVC-1000) using video tape[8] and states "In the literature, the most common definition of mass storage capacity is a trillion bits.".[9] The first IEEE conference on mass storage was held in 1974[10] and at that time identified mass storage as "capacity on the order of 1012 bits" (1 gigabyte).[11] In the mid-1970s IBM used the term to in the name of theIBM 3850 Mass Storage System, which provided virtual disks backed up byHelical scan magnetic tape cartridges, slower than disk drives but with a capacity larger than was affordable with disks.[12] The termmass 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:
Hard disk drives dominate storage media in terms of exabytes shipped and are projected to continue to so for this decade.[13]
Solid-state drives (i.e. Flash storage media) are the predominant storage media inpersonal computers.Flash memory (in particular,NAND flash) has an established and growing niche in high performance enterprise computing installations. Flash memory has also long been popular as removable storage such asUSB sticks, where it de facto makes up the market. Flash dominates incell phones.[14][15]
Tape is predominantly used for archival storage[16]
Optical discs are almost exclusively used in the physical distribution of retail software, music and movies because of the cost and manufacturing efficiency of the molding process used to produceDVD andcompact discs and the nearly-universal presence ofreader drives in personal computers and consumer appliances.[17]
The design ofcomputer architectures andoperating systems are often dictated by the mass storage andbus technology of their time.[18]
Mass storage devices used in desktop and most server computers typically have their data organized in afile system. The choice of file system is often important in maximizing the performance of the device: general purpose file systems (such asNTFS andHFS, for example) tend to do poorly on slow-seeking optical storage such as compact discs.
Somerelational databases can also be deployed on mass storage devices without an intermediate file system or storage manager.Oracle andMySQL, for example, can store table data directly on rawblock devices.
Onremovable media, archive formats (such astar archives onmagnetic tape, which pack file data end-to-end) are sometimes used instead of file systems because they are moreportable and simpler tostream.
On embedded computers, it is common tomemory map the contents of a mass storage device (usuallyROM or flash memory) so that its contents can be traversed as in-memory data structures or executed directly by programs.
In 2003, six years after introduction, there were over 250 million DVD playback devices worldwide, counting DVD players, DVD PCs, and DVD game consoles.
