METHOD FOR CREATING CLONE FILE, AND FILE SYSTEM ADOPTING THE SAME

• US 20130066930A1
• Filed: 09/14/2011
• Published: 03/14/2013
• Est. Priority Date: 09/14/2011
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Nakamura, Takaki, Kamei, Hitoshi
• Granted Patent: US 9,092,153 B2
• Time in Patent Office: Days
• US Class Current: 707/823
• CPC Class Codes: G06F 16/128 Details of file system snapshots on the file-level, e.g. snapshot creation, administration, deletion use of snapshots for error detection or correction G06F11/14, G06F11/16
• CPC Class Codes: G06F 16/162 Delete operations erasing in storage systems G06F3/0652
• CPC Class Codes: G06F 16/183 Provision of network file services by network file servers, e.g. by using NFS, CIFS network file access protocols H04L67/1097
• CPC Class Codes: G06F 16/1844 Management specifically adapted to replicated file systems
• CPC Class Codes: G06F 16/1873 Versioning file systems, temporal file systems, e.g. file system supporting different historic versions of files
• CPC Class Codes: G06F 3/061 Improving I/O performance
• CPC Class Codes: G06F 3/0643 Management of files
• CPC Class Codes: G06F 3/065 Replication mechanisms
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]

Abstract

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.

Claims

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 creates a first differential file while inhibiting update of the file upon receiving a request to create a clone of the file; and

accesses the first differential file upon receiving a request to access the clone;

wherein when the access 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 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 said file, the data is read therefrom, and when an update request of said file occurs, a second differential 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.

2. The file server according to claim 1, wherein the file system program creates a second differential file together with the first differential file regardless of whether an update request of the file occurs upon receiving a copy file creation request of the file, and accesses the second differential file upon receiving an access request to the file;

wherein when the access is (1) an update request;

(1a) if a disk block of the storage system is not assigned to a file block of the second differential file designated via the update request, a disk block of the storage system is assigned and update data is written thereto;

(1b) if a disk block is assigned to the file block, update data is written thereto;

wherein when the access is (2) a read request;

(2a) if data exists in the file block of the second differential file designated via the read request, the data is read therefrom; and

(2b) if there is no data in the file block, and if data exists in the file block corresponding to said file, the data is read therefrom.

3. The file server according to claim 1, wherein the file system program creates a first data management table when a first update request is received to the first differential file after creating the first differential file;

and

stores in the first data management table an offset of a file data including the update data, a start block position of a disk block of the storage system assigned to the file block of the first differential file designated via the update request, and a data block length of the file.

4. The file server according to claim 1, wherein the file system program creates a second data management table when a first update request is received to the second differential file after creating the second differential file;

and

stores in the second data management table an offset of a file data including the update data, a start block position of a disk block of the storage system assigned to the file block of the second differential file designated via the update request, and a data block length of the file.

5. The file server according to claim 2, wherein the file system program creates a second data management table when a first update request is received to the second differential file after creating the second differential file;

and

stores in the second data management table an offset of a file data including the update data, a start block position of a disk block of the storage system assigned to the file block of the second differential file designated via the update request, and a data block length of the file.

6. The file server according to claim 1, wherein the first differential file has a metadata, and the metadata includes information indicating that the first differential file is a clone.

7. The file server according to claim 2, wherein the first differential file has a metadata, and the metadata includes information indicating that the first differential file is a clone.

8. The file server according to claim 1, wherein the file system program is designed to create the first differential file each time a request to create a clone of the file is received;

and

wherein the file has a metadata, and the metadata includes information indicating that the file is a source of a clone and the number of files of the first differential file.

9. The file server according to claim 1, wherein the file system program

(1) deletes the second differential file upon receiving a delete request of the file, and sets the file so that it is not visible from the client terminal;

and

(2) deletes the first differential file upon receiving a delete request of the first differential file.

10. The file server according to claim 2, wherein the file system program

(1) deletes the second differential file upon receiving a delete request of the file, and sets the file so that it is not visible from the client terminal;

and

(2) deletes the first differential file upon receiving a delete request of the first differential file.

11. A computer system comprising:

a file server;

a management terminal connected to the file server; and

a storage system connected to the file server;

wherein the file server comprises;

a processor; and

a memory storing a file system program managing a file;

wherein the file system program creates a first differential file while inhibiting update of the file upon receiving a request to create a clone of the file; and

accesses the first differential file upon receiving a request to access the clone;

wherein when the access 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 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 said file, the data is read therefrom, and when an update request of said file occurs, a second differential 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.

12. The computer system according to claim 11, wherein the file system program creates a second differential file together with the first differential file regardless of whether an update request of the file occurs upon receiving a copy file creation request of the file;

and

accesses the second differential file upon receiving an access request to the file;

wherein when the access is (1) an update request;

(1a) if a disk block of the storage system is not assigned to a file block of the second differential file designated via the update request, a disk block of the storage system is assigned and update data is written thereto;

(1b) if a disk block is assigned to the file block, update data is written thereto;

wherein when the access is (2) a read request;

(2a) if data exists in the file block of the second differential file designated via the read request, the data is read therefrom; and

(2b) if there is no data in the file block, and if data exists in the file block corresponding to said file, the data is read therefrom.