File deduplication in a file system

• US 9,256,610 B2
• Filed: 06/27/2012
• Issued: 02/09/2016
• Est. Priority Date: 10/25/2010
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Tosaka, Eiji
• Primary Examiner(s): Mofiz, Apu
• Assistant Examiner(s): DAYE, CHELCIE L
• Application Number:
  US13/534,735
• Publication Number:
  US 20120271800A1
• Time in Patent Office: 1,322 Days
• Field of Search: 707/641, 707/692, 707/654
• US Class Current: 1/1
• CPC Class Codes: G06F 11/1453 using de-duplication of the data
• CPC Class Codes: G06F 11/1464 for networked environments
• CPC Class Codes: G06F 16/13 File access structures, e.g. distributed indices arrangements of input from, or output to, record carriers G06F3/06
• CPC Class Codes: G06F 16/162 Delete operations erasing in storage systems G06F3/0652
• CPC Class Codes: G06F 16/1748 De-duplication implemented within the file system, e.g. based on file segments de-duplication techniques in storage systems for the management of data blocks G06F3/0641
• CPC Class Codes: G06F 16/2365 Ensuring data consistency and integrity
• CPC Class Codes: G06F 2201/84 Using snapshots, i.e. a logical point-in-time copy of the data

Abstract

Each file is assigned in advance with a WWUID, newly assigned to a file upon the creation or update of the file and inherited from a file to a copied file when it is copied. In a backup apparatus, a file name reception unit receives the file name of a backup target file. A WWUID reception unit receives a WWUID corresponding to the file name. A WWUID search unit searches for the same WWUID in backup management information of a previous day stored in a backup destination. Only if the search is failed, a file operation instruction unit instructs the storing of the backup target file into the backup destination. Then, an Rcnt update instruction unit instructs the updating of the number of references made to the WWUID within the backup destination. A second management information update instruction unit then instructs updating of backup management information of the current day.

Claims

1. A method for file deduplication in a file system by a processor, comprising:

receiving one of a new file creation instruction, a file copy instruction, and a file update instruction specifying at least a file directory and a file name;

storing or updating inode information for a file upon creation, copying, or update of the file;

acquiring identification information which is newly assigned to the file upon creation, copying, or update of the file and is inherited by the file from a different file if the file is a copy of the different file, to thereby make a content of the file identifiable, wherein the identification information includes world wide unique identification (WWUID);

storing the identification information and an inode information number in the file directory;

storing the file name together and the identification information in an extended directory;

determining whether or not first identification information and second identification information match each other, the first identification information being the identification information acquired by the acquisition unit and assigned to a first file, the second identification information being the identification information acquired by the acquisition unit and assigned to a second file;

if the first identification information is determined to match the second identification information, preventing the first file and the second file from being stored as duplicate files in the file system;

registering, in count information, an increase in the number of pieces of identification information associated with the first file, when the second identification information becomes associated with the first file, the count information indicating the number of pieces of identification information associated with the first file, wherein the count information is a reference count number of the WWUID;

registering, in the count information, a decrease in the number of pieces of identification information associated with the first file, in response to an instruction to delete the first management information; and

deleting the first management information in response to the instruction to delete the first management information, and to also delete the first file if the count information after the registration by the second registration unit indicates that no identification information is associated with the first file.

2. The method according to claim 1, further comprising:

acquiring the first identification information assigned to the first file backed up to the file system at a first time point, from first management information for managing each file backed up to the first system at the first time point; and

acquiring the second identification information assigned to the second file to be backed up to the file system at a second time point subsequent to the first time point, and

if the first identification information and the second identification information match each other, preventing the first and second identification information from being copied to the file system at the second time point and that the second identification information is included in second management information and associated with the first file, the second management information for managing each file backed up at the second time point.

3. The method according to claim 1, further comprising

acquiring the first identification information assigned to the first file stored in a server computer, from first management information for managing each file stored in the server computer,

acquiring the second identification information assigned to the second file stored in a client computer, from second management information for managing each file stored in the client computer, and

if the first identification information and the second identification information match each other, deleting the second file from the client computer.

4. The method according to claim 1, further comprising:

acquiring the first identification information assigned to the first file stored in a server computer, from management information for managing each file stored in the server computer; and

acquiring the second identification information from data in an electronic mail received by a client computer, the second identification information being assigned to the second file attached to the electronic mail, and

if the first identification and the second identification match each other, preventing the second file from being saved in the client computer.