Patent ID: 7895394

Claim:
A storage system for managing volumes to which storage extents of at least a portion of a plurality of magnetic disk storage apparatuses are allocated, comprising: a request reception unit which receives an erasure process request to erase data stored in a first storage extent allocated to a volume; a storage extent detection unit which detects as a second storage extent, a storage extent in which data erasure has been carried out in advance, wherein the data erasure includes writing dummy data to the entire second storage extent, and wherein the second storage extent is different from the first storage extent allocated to the volume; an allocation unit which allocates the second storage extent to the volume, in place of the first storage extent; a notification transmission unit, which after allocation of the second storage extent to the volume, sends a notification to a source of the erasure process request, the notification indicating that access to the volume is possible; and a first data erasure unit, which after the notification indicating that access to the volume is possible has been sent, erases the data stored in the first storage extent.