Patent ID: 7801920

Claim:
A method of processing data in a computer system comprising at least one host and at least one storage system, the method comprising: receiving a request, from the host, to delete a unit of data stored on the storage system; in response to the request, determining whether a previously-defined retention period for the unit of data has expired by: retrieving first information, associated with the unit of data, that identifies second information specifying the previously-defined retention period for the unit of data, wherein the first information is separate from the second information and includes information identifying a retention class to which the unit of data belongs, wherein the second information is the previously-defined retention period for the retention class that defines a period of time during which units of data belonging to the retention class cannot be deleted from and/or modified on the at least one storage system, and wherein the at least one storage system stores a record associating a plurality of previously-defined retention periods with a plurality of retention classes; and using the first information and the record stored on the at least one storage system to retrieve the second information specifying the previously-defined retention period for the unit of data; receiving, at the at least one storage system, a second request requesting that the at least one storage system modify the retention period of the retention class; and when it is determined that the retention period for the unit of data has not expired, denying the request to delete the unit of data.