Patent ID: 7139875
Filing Date: 2006-11-21
Classification: G06F

Abstract:
1. A disk array apparatus comprising: a host interface which is connected to a host apparatus and receives data from the host apparatus; a memory which is connected to the host interface and stores data to be exchanged with the host apparatus and control information on the data to be exchanged with the host apparatus; plural disk interfaces which are connected to the memory and perform control such that the data to be exchanged with the host apparatus is read from and written in the memory; plural disk drives which are connected to the plural disk interfaces and in which the data sent from the host apparatus is stored under the control of the plural disk interfaces; and a control processor which controls reading and writing of data with respect to a first logical volume which is generated using storage areas of the plural disk drives, performs control such that data in the first logical volume prior to being updated by the writing of update data into the first logical volume, is copied and written in a second logical volume as differential data for each generation, and manages the differential data by providing a snapshot management table, which manages a relation among differential data for each generation stored in the second logical volume, in an area of the memory, wherein the control processor manages an amount of data stored in the second logical volume, increases a capacity of the second logical volume if the amount of data stored in the second logical volume has exceeded a first ratio of the capacity of the second logical volume, and reduces the capacity of the second logical volume to make it possible to use the reduced capacity of the second logical volume in other applications if the amount of data stored in the second logical volume has decreased to be less than a second ratio of the capacity of the second logical volume.