Method for creating clone file, and file system adopting the same

摘要

In the prior art clone creating technique of a file, a management table of a snapshot and the file was created when creating the clone file, so that a considerable amount of creation time for creating the clone file and storage capacity was required. In order to solve the problems of the prior art, the present invention provides a system wherein if a request to create a clone of a file is received, a differential file is created while inhibiting update of the file, and update data is written to the differential file. Further, when a first update request is received to the differential file after creating the differential file, a management table is created. According to the invention, a large amount of clone files can be created speedily.

主权项

1. A file server connected to a client terminal and a storage system, the file server comprising:
a processor; and a memory storing a file system program for managing a file; wherein the file system program
upon receiving a request to create a clone of a source file, which virtually provides the same data of the source file to the client terminal, creates a first differential file based on the source file while inhibiting update of the source file, the first differential file indicating differences between the source file at the time of receiving the request to create the clone and the clone of the source file; andaccesses the first differential file in response to receiving an access request to the clone from said client terminal, thereby providing the clone of the source file to the client terminal; wherein when the received access request is (1) an update request:
(1a) if a disk block of the storage system is not assigned to a file block of the first differential file designated via the update request, a disk block of the storage system is assigned to the file block and update data is written thereto;(1b) if a disk block of the storage system is assigned to the file block, update data is written thereto; wherein when the access request is (2) a read request:
(2a) if data exists in the file block of the first differential file designated via the read request, the data is read therefrom;(2b) if there is no data in the file block, and if data exists in the file block corresponding to the source file, the data is read therefrom, and when an update request to the source file is received from said client terminal, a second differential file based on the source file is created, and a disk block of the storage system is assigned to the file block of the second differential file designated via the update request and update data is written thereto.