Patent ID: 7707151

Claim:
A method for performing data migration in a computer system including at least one host and at least one storage system that stores data written by the host, the at least one storage system providing a plurality of storage volumes to the host to store data written by the host, the plurality of storage volumes including at least one first storage volume and at least one second storage volume, the method comprising acts of: (A) migrating data from the at least one first storage volume to the at least one second storage volume, the at least one first storage volume being allocated to at least one application program in the computer system to store data; (B) maintaining the at least one first storage volume available to the at least one application program so that write operations from the at least one application program can be performed to the at least one first storage volume during the act of migrating, wherein the act (A) comprises, at least one point in time during the migration, an act of storing, in a non-volatile storage medium, state information indicating a portion of a data set of the at least one first storage volume successfully copied to the at least one second storage volume at the at least one point in time, and wherein the act (A) comprises acts of reading the data from the at least one first storage volume to the at least one host, and writing the data from the at least one host to the at least one second storage volume; and (C) resuming, after an interruption that results in a loss of at least some state information stored in at least one volatile storage medium in the computer system, the act of migrating without restarting from the beginning of the data set, the act of resuming being performed using the state information stored in the non-volatile storage medium.