Data migration in cluster environment using host copy and changed block tracking

A non-transitory computer readable medium having computer program instructions recorded thereon, the computer program instructions including first instructions executable by a first host computer and second instructions executable by each of second host computers to cause the first and second host computers to perform respective parts of a method of migrating data from a source LUN to a target LUN in a data processing system having a cluster of multiple host computers and a storage subsystem containing the source LUN and the target LUN, the data being accessed concurrently by applications of the host computers using an association mechanism in each of the host computers initially associating the data with the source LUN as the location of the data in the system, the method including:

• performing a synchronization as iterations of concurrent operations at the host computers, a first iteration including a copy sweep by a first host computer to copy all existing data blocks of the source LUN to the target LUN, the first iteration and each subsequent iteration including at each of second host computers recording the locations of data blocks changed by application writes to the source LUN, the recording employing a respective changed-block record of the respective second host computer, each subsequent iteration also including, for each data block location identified in the changed-block record of each of the second host computers for the preceding iteration, copying the corresponding data blocks of the source LUN to the target LUN;
• and
• upon completion of the synchronization, performing a commitment including a final iteration and a transition to operation with the target LUN, the final iteration including, for a final set of recorded locations of data blocks in the changed-block record of each of the second host computers, copying the corresponding data blocks of the source LUN to the target LUN, the transition including at each host computer disabling application access to the source LUN and modifying the association mechanism to newly associate the data with the target LUN as the location of the data in the system.

A data processing system, comprising:

• a cluster of host computers including a first host computer and one or more second host computers;
• and
• a storage subsystem coupled to the cluster of host computers, the storage subsystem containing a source LUN and a target LUN, the source LUN storing data being accessed concurrently by applications of the host computers using an association mechanism in each of the host computers initially associating the data with the source LUN as the location of the data in the system,
• wherein the first and second host computers are operative to perform respective parts of a method of migrating the data from the source LUN to the target LUN, the method including:
• performing a synchronization as iterations of concurrent operations at the host computers, a first iteration including a copy sweep by a first host computer to copy all existing data blocks of the source LUN to the target LUN, the first iteration and each subsequent iteration including at each of second host computers recording the locations of data blocks changed by application writes to the source LUN, the recording employing a respective changed-block record of the respective second host computer, each subsequent iteration also including, for each data block location identified in the changed-block record of each of the second host computers for the preceding iteration, copying the corresponding data blocks of the source LUN to the target LUN;
• and
• upon completion of the synchronization, performing a commitment including a final iteration and a transition to operation with the target LUN, the final iteration including, for a final set of recorded locations of data blocks in the changed-block record of each of the second host computers, copying the corresponding data blocks of the source LUN to the target LUN, the transition including at each host computer disabling application access to the source LUN and modifying the association mechanism to newly associate the data with the target LUN as the location of the data in the system.