1) Primary storage, also known as main storage or memory, is the area in a computer in which data is stored for quick access by the computer's processor. The terms random access memory (RAM) and memory are often as synonyms for primary or main storage.
Primary storage is volatile and can be contrasted with non-volatile secondary storage, also known as auxiliary storage. The terms main storage and auxiliary storage originated in the days of the mainframe computer to distinguish the more immediately accessible data storage from data stored on punch cards that required input/output (I/O) operations. In the days when mainframe data storage contained ferrite cores, the term core storage was often used in place of primary storage.
2) In the enterprise, the label primary storage is often used to describe storage for data that is in active use, as opposed to data at rest in a backup. In this usage, the label primary storage may actually be describing the non-volatile secondary storage referred to in meaning 1 above. It should be noted that although these two meanings conflict, the appropriate meaning is usually apparent from the context. For example, primary storage in a tiered-storage architecture might consist of hard disks or flash-based solid state drives on a centralized storage-area network (SAN) or network-attached storage (NAS) array that stores transactional data or mission-critical application data that requires extremely high performance.
Deduplication and single instance storage cut primary data storage costs