Mass storage
Mass storage refers to large, persistent computer data storage devices.
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Mass storage is the persistent, machine-readable retention of large data volumes. The word "mass" typically means large compared to the hard disk drives of the same era, though it has also described storage that is large relative to primary memory—for instance, floppy disks on personal computers. Devices and systems classified as mass storage include tape libraries, RAID systems, hard disk drives, magnetic tape drives, magneto-optical disc drives, optical disc drives, memory cards, and solid-state drives, along with experimental types such as holographic memory. Both removable and non-removable media are included, but random access memory is not.
Mass storage falls into two broad categories: local data on devices like smartphones and computers, and enterprise servers and data centers that support the cloud. In local storage, solid-state drives are gradually replacing hard disk drives. In mobile devices—from phones to notebooks—most systems now rely on NAND flash. Enterprise and data center environments use storage tiers that combine SSDs and HDDs.
Definition
What counts as "large" depends heavily on the time period and market segment. Storage capacities have grown by many orders of magnitude since the late 1940s and continue to increase, but at any given time, common mass storage devices have been both much larger and much slower than typical primary storage. At the 1966 Fall Joint Computer Conference, the term referred to devices substantially larger than contemporary hard drives. A 1972 analysis identified mass storage systems from Ampex, Precision Industries, and International Video, noting that the most common definition of mass storage capacity was a trillion bits.
The first IEEE conference on mass storage in 1974 defined it as capacity on the order of 10¹² bits (one gigabyte). In the mid-1970s, IBM used the term for its 3850 Mass Storage System, which offered virtual disks backed by helical scan magnetic tape cartridges—slower than disk drives but with greater capacity than was affordable with disks. In the PC market, the term was applied to devices like floppy disk drives that were far smaller than what qualified as mass storage in mainframes.
Mass storage devices are characterized by sustainable transfer speed, seek time, cost, capacity, and storage media.
Background
The concept of mass storage emerged in the 1960s, with papers at the 1966 Fall Joint Computer Conference using the term for devices substantially larger than contemporaneous hard disk drives. A 1972 analysis identified several mass storage systems, including Ampex's Terabit Memory using video tape, Precision Industries' Unicon 690-212 using lasers, and International Video's IVC-1000 using video tape, and noted that the most common definition of mass storage capacity at that time was a trillion bits.
The first IEEE conference on mass storage in 1974 defined it as capacity on the order of 10^12 bits (1 gigabyte). In the mid-1970s, IBM introduced the IBM 3850 Mass Storage System, which provided virtual disks backed up by helical scan magnetic tape cartridges, slower than disk drives but with larger capacity than was affordable with disks. The term was also used in the PC marketplace for devices such as floppy disk drives, which were far smaller than devices not considered mass storage in the mainframe marketplace.
Storage media
Hard disk drives dominate storage media in terms of exabytes shipped and are projected to continue to do so for this decade. Solid-state drives (Flash storage media) are the predominant storage media in personal computers, and flash memory (particularly NAND flash) has an established and growing niche in high-performance enterprise computing installations. Flash memory has long been popular as removable storage such as USB sticks, where it de facto makes up the market, and dominates in cell phones.
Tape is predominantly used for archival storage, while optical discs are almost exclusively used in the physical distribution of retail software, music, and movies due to 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. 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. In the mobile segment from phones to notebooks, the majority of systems today is based on NAND Flash. For enterprise and data centers, storage tiers have been established using a mix of SSD and HDD. The design of computer architectures and operating systems is often dictated by the mass storage and bus technology of their time.
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Sources
Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.
- Wikipedia: Mass storage (CC BY-SA 4.0).
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