In order to decrease the overall cost of storing large amounts of data,
systems have been developed that use a hierarchy of storage devices from
fast local disks to archival off-line storage. Such storage devices may be
managed in a hierarchy where data that is accessed only infrequently can
be moved to archival storage. The present invention relies on a tight
integration of a hierarchical storage manager into the I/O system so that
remotely stored attributes can be identified and tracked internally to the
I/O system just like any other attributes. Implementations of the present
invention may rely on a layered driver model where lower level drivers
detect the existence of files with remotely stored attributes and then
transfer control for processing I/O requests involving files with remotely
stored attributes to higher level drivers. The higher level drivers then
assume control to finish processing the I/O request.