Patent ID: 7502903

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 (hereafter “the region moves”) while the data storage system remains online to a host device, the data storage system providing a virtual volume to the host device, the virtual volume being initially mapped to the source LD regions in one or more logical disks, the source LD regions being mapped to physical storage regions in one or more physical storage devices, the method comprising: generating a task comprising a list of the region moves to process for transferring data from the source LD regions to the target LD regions; and, processing the task, comprising: selecting a region move from the task, the region move comprises a transfer of data from a source LD region to a target LD region; determining if the region move would create excessive load on the corresponding physical storage devices so that the data storage system appears offline to the host device; and when the region move would create excessive load: determining if there is at least one region move in the task that has not been selected before; when there is at least one region move in the task that has not been selected before, repeating said processing for a next region move in the task; and when there is not at least one region move in the task that has not been selected before, waiting for another region move from the task that is currently being performed to finish and then repeating said processing for the next region move in the task.