Patent ID: 8909891

Claim:
A method of data storage, comprising: providing a plurality of physical storage devices, each device comprising memory units; allocating the memory units to create a plurality of logical volumes that form a volume group to virtualize a single storage system, each logical volume assigned a different volume serial number; allocating regular data sets to reside on one or more of the logical volumes in the volume group, a plurality of said logical volumes in the volume group including memory units to which data has not been allocated; creating a virtual logical volume by reallocating memory units previously allocated across a plurality of said logical volumes in said volume group from only those previously allocated memory units in said volume group to which data has not been allocated to reuse that physical storage device space; assigning a different volume serial number to said virtual logical volume; mapping the memory units in the virtual logical volume to the memory units in the plurality of logical volumes that constitute the virtual logical volume represented by the same physical storage so that each of these memory units belongs to both the virtual logical volume and one of the logical volumes from which the logical volume is created and the sizes of the volume group and the storage system remain unchanged by the creation of the virtual logical volume; reserving the virtual logical volume for only special data sets that must reside in a single logical volume thereby reducing the amount of memory in the volume group that is available for allocation to regular data sets that may reside on one or more logical volumes; and upon receipt of a special data set that must reside in a single logical volume, attempting to allocate the special data set to one of the logical volumes in the volume group, and if the allocation fails allocating the special data set to the virtual logical volume so that said special data set belongs to both the virtual logical volume and to each of the logical volumes from which the virtual logical volume is created.