Volatile storage is storage which fails when there is a power failure. Cache, MAIN memory, and REGISTERS are examples of volatile storage. Nonvolatile storage is storage which retains its content despite power FAILURES. An example is magnetic disk. Stable storage is storage which theoretically survives any kind of failure (short of a complete disaster!). This type of storage can only be approximated by replicating DATA.

In terms of I/O cost, volatile memory is the fastest and non-volatile storage is typically several times SLOWER. Stable storage is slower than non-volatile storage because of the cost of data replication.

Volatile storage is storage which fails when there is a power failure. Cache, main memory, and registers are examples of volatile storage. Nonvolatile storage is storage which retains its content despite power failures. An example is magnetic disk. Stable storage is storage which theoretically survives any kind of failure (short of a complete disaster!). This type of storage can only be approximated by replicating data.

In terms of I/O cost, volatile memory is the fastest and non-volatile storage is typically several times slower. Stable storage is slower than non-volatile storage because of the cost of data replication.