Patent ID: 8533409

Claim:
A storage virtualization computer system, comprising: a host unit for sending an I/O request; an external storage virtualization controller (SVC), coupled to the host unit, for executing an I/O operation in response to the I/O request; and at least one physical storage device (PSD) coupled to the SVC via a serial attached small computer system interface (SCSI) interconnect for providing data storage space to the storage virtualization computer system via the SVC; wherein the external SVC executes a snapshot function for storing the data state of at least one Source-Volume consisting of the at least one PSD at a particular moment, and said snapshot function is performed via a section allocation system (SAS), said SAS comprises a section allocation table (SAT) and at least one block association set (BAS), said BAS is a basis for performing a point-in-time backup (PIT backup), wherein said SAT comprises a first folder table which records the information which points to each said BAS and information about the Source-Volume which is associated with each said BAS, and when receiving a first write request that writes first data into a first location in said Source-Volume, a copy-on-write procedure is performed to copy data originally stored in data blocks.