Patent ID: 7761732

Claim:
A method, comprising: receiving, by a storage control unit from a host, a command for writing data to a first storage location, wherein the command includes an identifier; determining, by the storage control unit, whether the identifier in the command received from the host indicates that data protection is turned on, wherein if data protection turned on then any previously written data to the first storage location is to be copied for potential retrieval before the data is written to the first storage location; in response to determining, by the storage control unit, that the identifier in the command received from the host indicates that data protection is turned on, performing: determining, by the storage control unit, that previously written data is stored in the first storage location; copying, by the storage control unit, the previously written data to a second storage location, in response to determining that the previously written data is stored in the first storage location, wherein the first storage location and the second storage location are maintained in the storage control unit, and wherein the storage control unit includes data structures that include correspondences of selected data stored in the second storage location to the selected data stored in the first storage location at a selected time; and writing, by the storage control unit, the data to the first storage location, in response to copying the previously written data to the second storage location; and in response to determining, by the storage control unit, that the identifier in the command received from the host indicates that data protection is not turned on, performing: writing, by the storage control unit, the data to the first storage location.