Patent ID: 8904129

Claim:
A method of reading and writing data in an information system having a storage apparatus having one or more disk drives and a controller for providing a volume for storage, the volume being logically divided into multiple segments to which chunk data are able to be independently allocated, wherein the information system manages first chunk information to identify whether or not each segment is allocated to chunk data, the method comprising the steps of: in a backup process, transferring the first chunk information from the storage apparatus to a backup storage apparatus, checking the first chunk information to identify whether each segment is allocated to chunk data or not, if a segment is allocated to chunk data, transferring data read out from the segment to the backup storage apparatus, and if a segment is not allocated to chunk data, transferring neither default void pattern data nor data stored in the segment to the backup storage apparatus; and in a restore process, checking the first chunk information transferred from the storage apparatus to the backup storage apparatus to identify whether each segment is allocated to chunk data or not, if a segment is allocated to chunk data, restoring data from the backup storage apparatus to the storage apparatus, and if a segment is not allocated to chunk data, transferring neither default void pattern data nor data from the backup storage apparatus to the storage apparatus.