First ,STORAGE DEVICE CHARACTERISTICS
A storage device consists of a read/write mechanism and a storage medium. The storage medium is the device or substance that actually holds data. The read/write mechanism is the device used to read or write data to and from the storage medium. A device controller provides the interface between the storage device and system bus.
In some storage devices, the read/write mechanism and storage medium are a single unit using the same technology.
For example, most types of primary storage use electrical circuits implemented with semiconductors for both the read/write mechanism and storage medium. In other storage devices, the read/write mechanism and the storage medium use fundamentally different technologies.