At least one computer readable medium encoded with instructions that, when executed on a computer system, perform a method of accessing a unit of data stored in a storage environment (206; 305) that includes a plurality of storage clusters (207a, 207b; 307a, 307b), wherein the computer system comprises the storage environment and a host computer (201; 301) that stores data on the storage environment (206; 305), and wherein the method comprises acts of: receiving by the storage environment a request from the host computer (201; 301) to locate the unit of data previously stored in the storage environment (206; 305); and in response to receipt of the request, determining on which one of the plurality of storage clusters (207a, 207b; 307a, 307b) the unit of data is stored; wherein the storage environment (206; 305) is a content addressable storage environment in which the unit of data stored in the storage environment is accessible by a content address that is based, at least in part, upon at least a portion of the content of the unit of data, and wherein the act of determining further comprises determining on which of the plurality of storage clusters (207a, 207b; 307a, 307b) the unit of data is stored based on the content address of the unit of data wherein the content address is used in communication between the host computer and the storage environment to refer to the unit of data characterized in that: the content address includes time information, based on when the unit of data was stored in the storage environment (206; 305), and the act of determining comprises an act of determining on which of the plurality of storage clusters (207a, 207b; 307a, 307b) the unit of data is stored based, at least in part, on the time information of the content address of the unit of data. wherein the time information is used to index into maintained information indicating which of a plurality of algorithms to determine on which storage cluster a unit of data is to be stored was used during which period of time and to apply the indexed algorithm to an appropriate portion of the content address of the unit of data to determine on which of the plurality of storage clusters the unit of data is stored. receiving by the storage environment a request from the host computer (201; 301) to locate the unit of data previously stored in the storage environment (206; 305); and in response to receipt of the request, determining on which one of the plurality of storage clusters (207a, 207b; 307a, 307b) the unit of data is stored; wherein the storage environment (206; 305) is a content addressable storage environment in which the unit of data stored in the storage environment is accessible by a content address that is based, at least in part, upon at least a portion of the content of the unit of data, and wherein the act of determining further comprises determining on which of the plurality of storage clusters (207a, 207b; 307a, 307b) the unit of data is stored based on the content address of the unit of data wherein the content address is used in communication between the host computer and the storage environment to refer to the unit of data characterized in that: the content address includes time information, based on when the unit of data was stored in the storage environment (206; 305), and the act of determining comprises an act of determining on which of the plurality of storage clusters (207a, 207b; 307a, 307b) the unit of data is stored based, at least in part, on the time information of the content address of the unit of data. wherein the time information is used to index into maintained information indicating which of a plurality of algorithms to determine on which storage cluster a unit of data is to be stored was used during which period of time and to apply the indexed algorithm to an appropriate portion of the content address of the unit of data to determine on which of the plurality of storage clusters the unit of data is stored. the content address includes time information, based on when the unit of data was stored in the storage environment (206; 305), and the act of determining comprises an act of determining on which of the plurality of storage clusters (207a, 207b; 307a, 307b) the unit of data is stored based, at least in part, on the time information of the content address of the unit of data. wherein the time information is used to index into maintained information indicating which of a plurality of algorithms to determine on which storage cluster a unit of data is to be stored was used during which period of time and to apply the indexed algorithm to an appropriate portion of the content address of the unit of data to determine on which of the plurality of storage clusters the unit of data is stored.