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 the output of a hash function that is applied to at least a portion of the content of the unit of data, wherein the content address is used in communication between the host and the storage environment to refer to 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 of the unit of data comprises a time information indicating when the unit of data was stored in the storage environment; maintaining information indicating which of a plurality of algorithms used to determine on which storage cluster a unit of data should be stored was used during which period of time, wherein the maintained information is indexed by the time information; and using the time information to identify the indexed algorithm in the maintained information; and applying the indexed algorithm to the appropriate portion of the content address of the unit of data to determine on which of the plurality of 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 the output of a hash function that is applied to at least a portion of the content of the unit of data, wherein the content address is used in communication between the host and the storage environment to refer to 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 of the unit of data comprises a time information indicating when the unit of data was stored in the storage environment; maintaining information indicating which of a plurality of algorithms used to determine on which storage cluster a unit of data should be stored was used during which period of time, wherein the maintained information is indexed by the time information; and using the time information to identify the indexed algorithm in the maintained information; and applying the indexed algorithm to the appropriate portion of the content address of the unit of data to determine on which of the plurality of clusters the unit of data is stored. 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 of the unit of data comprises a time information indicating when the unit of data was stored in the storage environment; maintaining information indicating which of a plurality of algorithms used to determine on which storage cluster a unit of data should be stored was used during which period of time, wherein the maintained information is indexed by the time information; and using the time information to identify the indexed algorithm in the maintained information; and applying the indexed algorithm to the appropriate portion of the content address of the unit of data to determine on which of the plurality of clusters the unit of data is stored. 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 of the unit of data comprises a time information indicating when the unit of data was stored in the storage environment; maintaining information indicating which of a plurality of algorithms used to determine on which storage cluster a unit of data should be stored was used during which period of time, wherein the maintained information is indexed by the time information; and using the time information to identify the indexed algorithm in the maintained information; and applying the indexed algorithm to the appropriate portion of the content address of the unit of data to determine on which of the plurality of clusters the unit of data is stored.