The notion of "large" amounts of data is of course highly dependent on the time frame and the market segment, as mass 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. The term mass storage was used in the PC marketplace for devices far smaller than devices that were not considered mass storage in the mainframe marketplace. Mass storage devices are characterized by:
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 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. 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 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 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 so that its contents can be traversed as in-memory data structures or executed directly by programs.
