Patent ID: 8291245

Claim:
A data storage method comprising: storing data in a first memory; in response to the first memory exceeding a first threshold, migrating the data from the first memory to a second memory; in response to the second memory exceeding a second threshold, then activating a third memory if the third memory is inactive; in response to the second memory exceeding a third threshold greater than the second threshold, migrating the data from the second memory to a third memory; and rearranging a set of data units in the third memory into a plurality of memory groups based on last access time to each data unit; organizing the third memory into a plurality of memory sections, wherein the plurality of memory groups corresponding to said plurality of memory sections such that each memory section contains a group of said data units, and maintaining a memory section that contains a most recently accessed group of said data units in an active state, and deactivating one or more of the remaining memory sections; wherein the second memory is sized and configured to store data targeted for the third memory for maintaining a portion of the third memory in an inactive state.