Patent ID: 7281109

Claim:
A data migration method in a virtualization system coupled to at least one storage subsystem which stores data written by a host device, the at least one storage subsystem presenting at least one storage volume configured with a plurality of physical storages to the virtualization system, the virtualization system presenting at least one of virtual volumes as a storage resource to the host device, the data migration method comprising: mapping a first storage volume to a first virtual volume classified as a first tier, the first storage volume being configured with a plurality of physical storages in the virtualization system; mapping a second storage volume to a second virtual volume classified as a second tier, the second storage volume being configured with a plurality of physical storages in the virtualization system; managing the first virtual volume and the second virtual volume as a migration group; in response to receiving a migration instruction with the migration group, migrating data in the first storage volume to a third storage volume and data in the second storage volume to a fourth storage volume, the third and fourth storage volume being configured with a plurality of physical storages of the at least one storage subsystem, wherein a relationship of tier position between the third storage volume and the fourth storage volume is based on a relationship of tier position between the first tier and the second tier.