A method and apparatus for maintaining information in one or more virtual volume
aggregates comprising a plurality of virtual volumes. The method maintains a plurality
of virtual volumes in a first information storage medium, and forms one or more
virtual volume aggregates, where each of the of virtual volumes is assigned to
one of the virtual volume aggregates. The method further provides a plurality of
second information storage media. The method then identifies the least recently
used virtual volume, and writes the virtual volume aggregate comprising that least
recently used virtual volume to one or more second information storage media. Thereafter,
the method determines if space is required on said first information storage medium.
If space is required on said first information storage medium, the method selects
the virtual volume aggregate comprising the least recently used virtual volume
and removes from said first information storage medium each virtual volume in that
selected virtual volume aggregate that has been written to one or more second information
storage media.
