Patent ID: 7444489

Claim:
A method for a system manager in a data storage system to move data from source logical disk (LD) regions to target LD regions, the data storage system providing a virtual volume to a host device, the virtual volume being initially mapped to the source LD regions in one or more source logical disks, the source LD regions being mapped to physical storage regions in one or more physical storage devices, the method comprising: evaluating if moving data in the virtual volume from the source LD regions to the target LD regions would create excessive load on the physical storage devices associated with the source and the target LD regions so that the data storage system appears offline to the host device; when said moving would not create excessive load, moving data in the virtual volume from the source LD regions to the target LD regions; flushing dirty cache to the physical storage devices; determining if said flushing dirty cache is taking longer than a time limit so that the data storage system appears offline to the host device; and when said flushing dirty cache is not taking longer than the time limit, updating a mapping of the virtual volume from the source LD regions to the target LD regions.