Patent ID: 7882067

Claim:
A snapshot management device that obtains and manages a snapshot that is an image of a first volume at a certain point in time, the first volume being used by a user, the snapshot management device comprising: a central processing unit including: a snapshot obtaining unit that obtains a snapshot on a regular basis and manages the obtained snapshot; a difference amount detecting unit that detects the amount of difference between two snapshots obtained by the snapshot obtaining unit; and a snapshot deleting unit that deletes, from among the two snapshots, the snapshot obtained earlier than the other, when the difference amount detected by the difference amount detecting unit is smaller than a predetermined threshold value, and deletes, from among a plurality of the obtained snapshots, one of the snapshots that was obtained earliest among the plurality of snapshots if the most recently obtained snapshot cannot be mounted, wherein, before deleting a snapshot that would otherwise be deleted based on the difference amount or whether the most recently obtained snapshot cannot be mounted, the snapshot deleting unit judges whether or not to delete the snapshot based on whether the number of accessing users for the snapshot that would otherwise be deleted is smaller than a predetermined threshold, and wherein, if the snapshot deleting unit judges to delete the snapshot, the deleted snapshot is deleted by canceling mounting and file-sharing configuration executed by the snapshot deleting unit to prevent a user from referring to the deleted snapshot.