A memory/storage hierarchy in computer storage distinguishes each level in the hierarchy by:
The transfer of memory from primary storage to secondary storage is done through virtual memory.
There are three major storage levels
Secondary storage and On-line mass storage principally Disk storage – millions of cycles latency if not cached, but very large
Tertiary and Off-line bulk storage - several seconds latency, can be huge because it happens via a network connection.
The internal or external type of memory is a grouping by location of the memory.
When the memory is internal, it's on the motherboard, otherwise, it's external.
There is only one internal memory and it's the primary (main/internal).
Level | Type |
---|---|
Primary | Internal |
Secondary | External |
Tertiary | External |
Historically, memory and storage were respectively called main memory and auxiliary storage.
Auxiliary storage (or auxiliary memory units) is used to represent memory which are not directly accessible by the CPU (ie secondary or tertiary storage).
Memory can also be categorized by their volatility.