Patent ID: 7716441

Claim:
A data migration method in a virtualization system coupled to a plurality of storage subsystems which store data written by a host device, each of the plurality of storage subsystems presenting a data storing area configured with a plurality of physical storages as a storage resource to the virtualization system, the data migration method comprising: mapping a first portion of a data storing area as a first tier, the first portion of the data storing area being configured with a first plurality of physical storage; mapping a second portion of the data storing area as a second tier, the second portion of the data storing area being configured with a second plurality of physical storage; managing the first portion of the data storing area and the second portion of the data storing area as a migration group; and in response to receiving a migration instruction with the migration group, migrating data in the first portion of the data storing area to a third portion of the data storing area and migrating data in the second portion of the data storing area to a fourth portion of the data storing area, the third and fourth portions of the data storing area being configured respectively with a third plurality of physical storage and a fourth plurality of physical storage, wherein a relationship of tier position between the third portion of the data storing area and the fourth portion of the data storing area is based on a relationship of tier position between the first tier and the second tier.