Mass storage

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 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 considered mass storage in the mainframe marketplace. Mass storage devices are characterized by: • Sustainable transfer speed • Seek time • Cost • Capacity == Storage media ==

Hard disk drives dominate storage media in terms of exabytes shipped and are projected to continue to so for this decade. Solid-state drives (i.e. Flash storage media) are the predominant storage media in personal 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 as USB sticks, where it de facto makes up the market. Flash dominates in cell phones. Tape is predominantly used for archival storage 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 produce DVD and compact discs and the nearly-universal presence of reader drives in personal computers and consumer appliances. The design of computer architectures and operating systems are often dictated by the mass storage and bus technology of their time. == Usage ==

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. == See also ==