Efficient data migration in hierarchical storage management system

A computer system for managing copy operations on data units in a hierarchical storage management system, the management system comprising an upper layer and a lower layer, wherein the upper layer comprises a domain in which storage nodes are arranged for communication in a multiplexed grid configuration, wherein each data unit is stored in one or more of the storage nodes, the computer system comprising:

• one or more computer processors, one or more computer-readable storage media, and program instructions stored on one or more of the computer-readable storage media for execution by at least one of the one or more computer processors, the program instructions, when executed by the at least one of the one or more computer processors, causing the computer system to perform a method comprising:
• determining, an N value for each data unit that represents a total number of copies of the data unit stored in the domain, wherein the determination is made based on data received over the multiplexed grid from one or more of the storage nodes respectively storing the copies;
• scheduling copy operations with respect to each data unit based on comparison of the determined N value, wherein the scheduling copy operations comprises selecting a data unit from the nodes where the data unit have the determined N value less than any other N values before selecting another data unit from another node;
• and
• performing the copy operations in accordance with the scheduling with respect to each data unit for respective migration of each data unit to the lower layer.

A computer program product for managing copy operations on data units in a hierarchical storage management system, the management system comprising an upper layer and a lower layer, wherein the upper layer comprises a domain in which storage nodes are arranged for communication in a multiplexed grid configuration, wherein each data unit is stored in one or more of the storage nodes, the computer program product comprising:

• one or more computer-readable storage devices and program instructions stored on at least one of the one or more computer-readable storage devices for execution by at least one or more computer processors of a computer system, the program instructions, when executed by the at least one of the one or more computer processors, causing the computer system to execute instructions to perform a method comprising:
• determining, an N value for each data unit that represents a total number of copies of the data unit stored in the domain, wherein the determination is made based on data received over the multiplexed grid from one or more of the storage nodes respectively storing the copies;
• scheduling copy operations with respect to each data unit based on comparison of the determined N value, wherein the scheduling copy operations comprises selecting a data unit from the nodes where the data unit have the determined N value less than any other N values before selecting another data unit from another node;
• and
• performing the copy operations in accordance with the scheduling with respect to each data unit for respective migration of each data unit to the lower layer.