Patent ID: 7287045
Filing Date: 2007-10-23
Classification: G06F,Y10S

Abstract:
1. A backup method for use with a storage system, the storage system comprising: the network attached storage device comprising: a network interface connected to the network; a memory which stores a control program; a disk drive having an primary volume, a differential volume, and a mapping table, the primary volume storing data sent from the client, the differential volume storing differential data of a snapshot of the primary volume, the mapping table managing the relation between data stored in the primary volume and differential data stored in the differential volume, the mapping table including at least one changed/unchanged bit identifying whether differential data corresponding to the snapshot is stored on the differential volume, and also a storage address of the data in the primary volume and a storage address of the differential data of each snapshot, stored in correspondence relationship to one another, a disk interface connected to the disk drive to control data transfer between the client and the disk drive based on a data input/output request from the client; and a control processor which controls read and write of data in the primary volume created from a storage area of the disk drive, which controls to write data stored in the primary volume in the past in the differential volume as differential data for the respective generations, which uses the mapping table to manage, for the respective generations, the address relation between the storage address of the data stored in the primary volume and the storage address of the differential data stored in the differential volume, and which refers to the mapping table to compose the data of the primary volume and the differential data and to create a virtual volume for the respective generations, the backup method comprising the steps of: controlling the control processor to mount the virtual volume on a mount point in a file system; controlling the management client to request to the control processor to provide a list of the generations that can be backed up; causing the control processor to obtain a list of the generations that can be backed up by referring to the mapping table and checking whether the changed/unchanged bit is on or not, and to send the obtained list to the management client; controlling the management client to request to the control processor to take a backup of a generation selected from the obtained list; causing the control processor to obtain a path name, including the mount point of the virtual volume, designated with regard to the request to take the backup; controlling the control processor to determine the designated generation based on the obtained path name; controlling the control processor to search the mapping table for the designated generation and to obtain the address of data that constitutes the virtual volume; controlling the control processor to read data stored at the obtained address; and controlling the control processor to send the obtained data of the virtual volume to the media server.