A method for reducing data loss and unavailability by integrating multiple
levels of a storage hierarchy is provided. The method includes receiving
a read request. In addition, the method includes recognizing a data
failure in response to the read request. The method further includes
locating an alternate source of the data to be read in response to
recognizing the data failure. The alternate source includes data cached
at devices in the storage hierarchy, data in a backup system, and
cumulative changes to the data since the last backup. Moreover, the
method includes responding to the read request with data from the
alternate source.