As mass storage are in the IT range storage media refers to the large amounts of data permanently stored. According to this definition, volatile memories such as conventional RAM are not mass memories , regardless of their size.
Due to the general development in the computer sector, the term “large amount of data” naturally depends heavily on the current circumstances. Accordingly, a mass storage medium is understood to mean data carriers with ever increasing capacities over time. However, over the course of time, the mass storage device is larger and slower than the main memory used at the same time . Programs and data on a mass storage device are almost never processed directly by a main processor . For this purpose, they are first copied ("loaded") into the main memory and processed there. The results can then be written ("saved") back to the mass storage device if necessary.
Hard drives have been of greatest importance as mass storage for over thirty years . The development of their capacity has kept pace with the general development: at the beginning of the 1980s they could store 10 megabytes , today they can store several thousand gigabytes . Their speed has also increased significantly, but not to the same extent as their capacity. Solid state disks have been gaining in importance for a number of years .
Depending on the size definition, there are media such as punched cards , punched tapes , magnetic tapes , floppy disks , optical disks (including read - only CD-ROM , DVD -ROM and BD-ROM and their versions that can be written to one or more times) and flash memory media such as USB sticks and CompactFlash cards can also be described as mass storage devices. Your advantage is the simple mobility and usability as a removable medium in any device with a corresponding drive, slot or suitable interface .
In general, it is not only the capacity of mass storage that is of interest, but also the following factors, depending on the area of application:
- Latency : The average or maximum length of time that elapses from sending a data request to the mass storage device until a data transfer begins.
- Throughput : The amount of data that is transferred over a period of time.
- Average lifetime: The number of operating hours until the first data loss occurs (statistically).
- Access type: Mass storage media can be read or written to in sequential ( following ) or direct access ( optional ). Some media can only be written to once (see WORM ) and are suitable for archiving. Others are rewritable to a limited extent ( CD-RW / DVD-RW ), flash memory is almost unlimited and hard drives are unlimited. So-called ROM media are provided with data during production and can only be read.
- Mobility: Some mass storage devices are usually permanently installed, others can easily be exchanged.
- Networkability: There are several ways of making mass storage devices available in a computer network. On file servers , also known as network attached storage are called to be accessed at the file level. A storage area network is accessed at data block level. Both types can be integrated into existing networks. This means that no new hardware has to be built into existing systems.
- Security: Some mass storage devices offer their own password protection or the possibility of completely and irreversibly deleting the data stored on them without using the mass storage device, e.g. B. having to physically destroy it by shredding. This can be important for sensitive data.
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