A method, system, apparatus and computer program product for reducing the
number of physical storage systems needed for a volume group to remain
active are provided. This is accomplished by creating mirroring sets out
of the physical storage systems in the volume group and by setting up a
policy that so long as one mirror out of each mirror set is available, the
volume group should be allowed to remain active. To activate a volume
group (i.e., when the computer system is turned or reset), there have to
be at least one full mirror set and at least one mirror out of each
remaining mirror set available. These two policies guarantee that there
will always be valid metadata in the system.
