Patent ID: 7701700

Claim:
An apparatus comprising: an enclosure; a substrate mounted in the enclosure and having a first plurality of disk-drive connectors mounted to the substrate; and one or more processing units and memory mounted in the enclosure and operatively connected to the first plurality of disk-drive connectors, and configured to accommodate a fixed set of disk drives such that a plurality of the fixed set of disk drives cannot be replaced, wherein the fixed set of disk drives includes a variable number of spare disk drives that form a first subset of the fixed set of disk drives, and wherein the fixed set of disk drives also includes a second subset of operating disk drives, and wherein the second subset of operating disk drives define a stated total data-storage capacity for the apparatus, wherein the number of spare disk drives in the first subset is selected to provide a predetermined expected lifetime for the apparatus such that the expected lifetime of the apparatus is defined as a period of time that ends once the apparatus has run out of spare drives due to all of the number of spare drives having been reallocated to hold data from failed ones of the second subset of operating disk drives, and wherein the expected lifetime is variable and determined by the number of disk drives in the first subset.