Patent ID: 8209595

Claim:
A stored data quantity reduction method for a storage apparatus where a control program performs data check processing to verify data using verification information of a block included in the data, the stored data quantity reduction method comprising: a distinction step whereby the control program distinguishes the verification information, which is uniquely related to the block, from a data part included in the data from a host computer regarding the block written in a primary area, in response to a write request from the host computer; a calculation step whereby the control program executes a calculation for reducing a quantity of data stored in a storage device concerning the data part from the host computer; an elimination step whereby the control program performs data de-duplication by omitting to store the data if the data is substitutable with pre-stored data; a verification information storing step whereby the control program stores the verification information corresponding to the block in a pool volume after relating to the pre-stored data corresponding to the block without omitting to store the verification information; and a restoration step whereby the control program, when receiving a read request from the host computer, searches for the pre-stored data using the verification information of the block as a search key, and restores a block on the primary area based on the verification information and the pre-stored data.