CACHING OF METADATA FOR DEDUPLICATED LUNS

Efficient processing of user data read requests in a deduplicated data storage system places the metadata for most frequently requested data in data structures and locations in the system hierarchy where the metadata will be most rapidly available. The total amount of such metadata makes storing all of the metadata in high speed memory expensive, and the system and method described uses both the temporal and the spatial characteristics of the user system activity in any epoch to adjust the contents of metadata cache so as to respond to the dynamics of a multi user or multi-application environment where the storage system is not made aware of the time changing mix of operations except by observation of the individual requests. A history record is used to promote metadata from the slow memory to the fast memory, and a process selection may be adjusted based on the address-space activity.