FAILOVER METHOD OF REMOTELY-MIRRORED CLUSTERED FILE SERVERS

• US 20090177720A1
• Filed: 03/23/2009
• Published: 07/09/2009
• Est. Priority Date: 06/08/2006
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Kitamura, Manabu, Shitomi, Hidehisa
• Granted Patent: US 8,099,622 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 11/2092 Techniques of failing over between control units
• CPC Class Codes: G06F 11/2097 maintaining the standby controller/processing unit updated initialisation or re-synchronisation thereof G06F11/1658 and subgroups

Abstract

By incorporating a referral mechanism, a failover method and system for remotely mirrored clustered file servers enables a client computer to transparently access a remotely mirrored file system during a failover of a first NAS (network attached storage) storing the file system. The first NAS is clustered with a second NAS that takes over the IP address of the first NAS on failover. A mirroring relationship is established between the first NAS and a third NAS whereby a copy of the file system is replicated to the third NAS. A referral is created on the second NAS, such that an access attempt from the client computer for accessing the first file system that is directed to the second NAS following IP address takeover from the first NAS after failover is referred to the third NAS by the referral to enable the client computer to access the copy of the file system.

Claims

1. A method of controlling a plurality of file systems, said plurality of file systems includes a first, second, and third file system, said plurality of file systems are clustered and has a single namespace, comprising:

establishing a mirroring relationship between the first file system and the third file system, wherein a copy of the first file system is replicated to the third file system;

creating a first referral on the second file system, wherein an access request from a client computer directed to the second file system for accessing a file stored in the first file system is directed to the third file system by the first referral whereby the copy of the first file system is accessed;

directing access from said client computer to the third file system after the first file system receives a failback request from a management server,

wherein if said access from said client computer is read access, file is read from said third file system, and wherein if said access from said client computer is write access, data is written to said third file system and a replication of said data is written to the first file system.

2. The method of claim 1,

wherein an IP address of the first file system is taken over by the second file system so that the client computer directs requests to access the first file system to the second file system.

3. The method of claim 1, further comprising:

copying back the mirrored file system from the third file system to the first file system in response to said failback request from a management server;

directing access from said client computer to the first file system after said copying back operation is completed.

4. The method of claim 3, further comprising:

creating a second referral on the third file system and sending said second referral to said client computer after said copying back operation is completed,

wherein said directing access to the first file system is performed after said second referral is sent from said third file system to said client computer.

5. The method of claim 1,

wherein said creating said first referral on the second file system is performed after said management server issues a mirror establishing request to said first file system.

6. The method of claim 1,

wherein said establishing a mirroring relationship between the first file system and the third file system is performed in response to a request from said management server.