Patent ID: 8316203
Filing Date: 2012-11-20
Classification: G06F

Abstract:
1. A storage system for storage of data written from a computer, the storage system comprising: a memory medium that provides a physical memory area for data; and a control device that controls over data input/output to/from the memory medium, wherein a part of the physical memory area is provided by the control device to the computer as a first logical volume, wherein another part of the physical memory area is allocated to a pool region under the management of the control device, and wherein the control device: stores, when receiving a write request of data to the first logical volume, the data on request into the first logical volume, reads, when receiving a first-generation snapshot creation request, the data stored in the first logical volume at a time of receiving the first-generation snapshot creation request, and writes the data being a read result into the pool region as data corresponding to a first-generation snapshot, and reads, when receiving a second-generation snapshot creation request after receiving the first-generation snapshot creation request, from the data stored in the first logical volume at a time of receiving the second-generation snapshot creation request, any portion of the data updated after the first-generation snapshot creation request is received but before the second-generation snapshot creation request is issued, and writes the data being a read result into the pool region as data corresponding to a second-generation snapshot, wherein management information is stored for establishing a correlation between the data stored in the pool region and a snapshot generation, wherein if receiving a request from the computer for reading data including a designation of the snapshot generation, the control device reads data corresponding to a snapshot of the designated generation from the pool region for transmission to the computer, wherein the control device provides, to the computer, a second logical volume including a replica of the data stored in the first logical volume at the time of receiving the first-generation snapshot creation request, and a third logical volume including a replica of the data stored in the first logical volume at the time of receiving the second-generation snapshot creation request, wherein the management information includes information for establishing a correlation among the data stored in the pool region, the snapshot generation, and an address in the second logical volume and that in the third logical volume, and wherein the control device: reads, when receiving a request from the computer for reading the data in the second logical volume, from the data stored in the pool region, any portion of the data corresponding to the first-generation snapshot and to an address designated by the read request for transmission to the computer, reads, when receiving a request from the computer for reading the data in the third logical volume, from the data stored in the pool region, any portion of the data corresponding to the second-generation snapshot and to an address designated by the read request for transmission to the computer, and reads, when the pool region is not storing the data corresponding to the second-generation snapshot and to the address designated by the read request, from the data stored in the pool region, the portion of the data corresponding to the first-generation snapshot and to the address designated by the read request for transmission to the computer.