Patent ID: 8135677

Claim:
A file management system that is connected to a storage device and reads or writes data of a file from or in a first volume, which is provided by the storage device, in response to a request sent from a host computer, comprising: a snapshot creating unit that creates one snapshot or a plurality of snapshots which relates to the first volume and can be updated; and a file deleting unit that, in response to an externally issued designated file deletion command, deletes a designated file from all of the first volume and snapshots or part thereof specified in the deletion command, wherein: the file deleting unit overwrites the data items of the designated file in at least one of the first volume and the snapshots, from which the designated file should be deleted, with invalid data, and changes pieces of management information on the designated file into a reference-disabled state, wherein: when a file shared by the first volume and snapshot or by the plurality of snapshots is updated, the snapshot creating unit executes copying processing of copying the data of the file, which is obtained prior to the updating, into a second volume provided by the storage device; the file deleting unit changes the referencing destination of the designated file, which is specified in the management information on the designated file in the first volume or snapshot from which the designated file should be deleted, into the referencing destination of the designated file specified in the management information on the designated file in the first volume or snapshot designated as a base snapshot among at least one of the first volume and snapshots from which the designated file should be deleted, overwrites the referencing destination of the designated file, which is specified in the management information on the designated file in the at least one of the first volume and snapshot other than the base snapshot among the at least one of the first volume and snapshots from which the designated file should be deleted, with invalid data, and collects the storage area, in which the data of the designated file overwritten with the invalid data has been stored, as an unused area; the file deleting unit controls the snapshot creating unit so that the copying processing will be ceased; the file deleting unit overwrites the position of the data of the designated file, which is specified in the management information on the designated file in the first volume, with invalid data; the file deleting unit deletes the pieces of management information on the designated file in the at least one of the first volume and snapshots from which the designated file should be deleted; and the file deleting unit controls the snapshot creating unit so that the copying processing will be resumed.