Abstract: A method and device for performing a volume copy is provided. The volume copy method allows access to both the Volume Copy Source and Volume Copy Target while the volume copy process is occurring. This allows a system administrator to initiate a volume copy without worrying that host access to the Volume Copy Source and Volume Copy Target will be interrupted.

Abstract: Methods and apparatuses for providing a data storage system having snapshot restore capabilities are provided. In particular, snapshots may be taken to represent a state of a storage volume at different times. The state of the storage volume may be returned to the state represented by any snapshot even while the storage volume continues to accept read and write operations. Furthermore, these features are provided in the context of a sparse snapshot structure, according to which multiple copies of individual data chunks are not maintained by the data storage system.