DATA SYNCHRONIZATION AMONG FILE STORAGES USING STUB FILES

• US 20120150799A1
• Filed: 12/14/2010
• Published: 06/14/2012
• Est. Priority Date: 12/14/2010
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: MATSUZAWA, Keiichi
• Granted Patent: US 8,856,073 B2
• Time in Patent Office: Days
• US Class Current: 707/622
• CPC Class Codes: G06F 16/119 Details of migration of file systems migration mechanisms in storage systems G06F3/0647
• CPC Class Codes: G06F 16/1744 using compression, e.g. sparse files
• CPC Class Codes: G06F 16/178 Techniques for file synchronisation in file systems
• CPC Class Codes: G06F 16/1787 Details of non-transparently synchronising file systems
• CPC Class Codes: G06F 16/185 Hierarchical storage management [HSM] systems, e.g. file migration or policies thereof details of archiving G06F16/11
• CPC Class Codes: G06F 3/0607 by facilitating the process of upgrading existing storage systems, e.g. for improving compatibility between host and storage device
• CPC Class Codes: G06F 3/0647 Migration mechanisms
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]

Abstract

A method switches file server from old file server to new file server which are coupled via a backend network and provides data synchronization. The old file server and new file server are coupled with one or more host computers via a frontend network to direct input/output (I/O) requests from the one or more host computers. The method comprises creating stub files in the new file server, the stub files including stub information indicating location of data in the old file server; switching I/O requests directed to old file server to I/O requests directed to the new file server; checking whether the new file server has any stub files; and, if the new file server has one or more stub files, recalling data corresponding to the one or more stub files from the old file server according to the stub information to replace the one or more stub files.

Claims

1. A method for switching file server from an old file server to a new file server which are coupled via a backend network and for data synchronization, the old file server and the new file server being coupled with one or more host computers via a frontend network to direct input/output (I/O) requests from the one or more host computers, the method comprising:

creating stub files in the new file server, the stub files including stub information indicating location of data in the old file server;

switching I/O requests directed to the old file server to I/O requests directed to the new file server;

checking whether the new file server has any stub files; and

if the new file server has one or more stub files, recalling data corresponding to the one or more stub files from the old file server according to the stub information to replace the one or more stub files.

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

continuing I/O requests from the one or more host computers to the file servers during the switching, checking, and recalling.

3. The method according to claim 1, further comprising, prior to creating stub files in the new file server:

copying data from the old file server to a storage media and, after the copying is completed, installing the storage media containing the copied data in the new file server;

storing in the new file server a copy date timestamp corresponding to the copying of data from the old file server to the storage media;

checking a flag, corresponding to each file or directory in the new file server, as NO indicating that the data in the file or directory are not latest in the new file server;

performing the switching of I/O requests directed to the old file server to I/O requests directed to the new file server;

checking whether any file or directory in the new file server has a corresponding flag NO indicating that the data therein are not latest in the new file server; and

for each file or directory with a NO flag, checking the flag as YES in the new file server, and if the copy date timestamp for data in the file or directory is older than a target timestamp of the corresponding file or directory in the old file server indicating that data of the corresponding file or directory in the old file server has been overwritten at the target timestamp which is newer than the copy date timestamp, removing data of the file or directory in the new file server and performing the creating stub files in the new file server for the file or directory.

4. The method according to claim 3, wherein the method performs the following in parallel for different files or directories:

checking whether any file or directory in the new file server has a corresponding flag NO;

for each file or directory with a NO flag, checking the flag as YES in the new file server and removing data of the file or directory in the new file server and performing the creating stub files in the new file server for the file or directory; and

recalling data corresponding to the one or more stub files from the file server having the data according to the stub information to replace the one or more stub files if the new file server has one or more stub files.

5. The method according to claim 3, wherein an external file server is coupled with the new file server via the backend network, the method further comprising, after recalling data corresponding to the one or more stub files from the file server having the data according to the stub information:

migrating files of the recalled data to the external file server.

6. The method according to claim 5, wherein the method performs the following in parallel for different files or directories:

checking whether any file or directory in the new file server has a corresponding flag NO;

for each file or directory with a NO flag, checking the flag as YES in the new file server and removing data of the file or directory in the new file server and performing the creating stub files in the new file server for the file or directory;

recalling data corresponding to the one or more stub files from the file server having the data according to the stub information to replace the one or more stub files if the new file server has one or more stub files; and

migrating files of the recalled data to the external file server.

7. The method according to claim 1, wherein an external file server is coupled with the new file server via the backend network, the method further comprising, after recalling data corresponding to the one or more stub files from the file server having the data according to the stub information:

migrating files of the recalled data to the external file server.

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

receiving, by the new file server, an I/O request for a file from one of the one or more host computers;

determining whether the file of the I/O request is a stub file in the new file server;

if the file is not a stub file and the I/O request is not a write request, processing the I/O request to access data in the new file server;

if the file is a stub file and the I/O request is not a write request, recalling data corresponding to the stub file from the old file server according to the stub information to replace the one or more stub files; and

if the I/O request is a write request, writing data of the write request to the new file server.

9. The method according to claim 8, further comprising:

migrating data of the I/O request to an external file server.

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

creating one or more stub directories in the new file server, the one or more stub directories including stub information indicating location of data in one or more directories in the old file server;

receiving, by the new file server, an I/O request for a directory from one of the one or more host computers;

determining whether the directory of the I/O request is a stub directory in the new file server;

if the directory is not a stub directory and the I/O request is not a write request, processing the I/O request to access data in the new file server;

if the file is a stub directory and the I/O request is not a write request, recalling data corresponding to the stub directory from the old file server according to the stub information to replace the one or more stub files; and

if the I/O request is a write request, writing data of the write request to the new file server.

11. A new file server in an information system which includes an old file coupled with the new file server via a backend network;

one or more host computers; and

a frontend network coupling the one or more host computers with the old and new file servers;

the new file server comprising;

a processor;

a memory; and

a data synchronization module configured to

create stub files in the new file server, the stub files including stub information indicating location of data in the old file server, making it possible to switch I/O requests directed to the old file server to I/O requests directed to the new file server; and

upon receiving an I/O request by the new file server, check whether the new file server has any stub files and, if the new file server has one or more stub files, recall data corresponding to the one or more stub files from the old file server according to the stub information to replace the one or more stub files.

12. The new file server according to claim 11, further comprising:

a storage media containing data copied from the old file server and installed in the new file server;

wherein the memory stores a copy date timestamp corresponding to the copying of data from the old file server to the storage media;

wherein the new file server includes a hierarchical storage management module which is configured, prior to creating stub files in the new file server by the data synchronization module, to

check a flag, corresponding to each file or directory in the new file server, as NO indicating that the data in the file or directory are not latest in the new file server;

check whether any file or directory in the new file server has a corresponding flag NO indicating that the data therein are not latest in the new file server; and

for each file or directory with a NO flag, check the flag as YES in the new file server, and if the copy date timestamp for data in the file or directory is older than a target timestamp of the corresponding file or directory in the old file server indicating that data of the corresponding file or directory in the old file server has been overwritten at the target timestamp which is newer than the copy date timestamp, remove data of the file or directory in the new file server and create stub files in the new file server for the file or directory.

13. The new file server according to claim 12, wherein the new file server is configured to perform the following in parallel for different files or directories:

the hierarchical storage management module checking whether any file or directory in the new file server has a corresponding flag NO;

for each file or directory with a NO flag, the hierarchical storage management module checking the flag as YES in the new file server and removing data of the file or directory in the new file server and creating stub files in the new file server for the file or directory; and

the data synchronization module recalling data corresponding to the one or more stub files from the file server having the data according to the stub information to replace the one or more stub files if the new file server has one or more stub files.

14. The new file server according to claim 12,

wherein the data synchronization module is configured, after recalling data corresponding to the one or more stub files from the file server having the data according to the stub information, to migrate files of the recalled data to an external file server.

15. The new file server according to claim 14, wherein the new file server is configured to perform the following in parallel for different files or directories:

the hierarchical storage management module checking whether any file or directory in the new file server has a corresponding flag NO;

for each file or directory with a NO flag, the hierarchical storage management module checking the flag as YES in the new file server and removing data of the file or directory in the new file server and performing the creating stub files in the new file server for the file or directory;

the data synchronization module recalling data corresponding to the one or more stub files from the file server having the data according to the stub information to replace the one or more stub files if the new file server has one or more stub files; and

the data synchronization module migrating files of the recalled data to the external file server.

16. The new file server according to claim 11,

wherein the data synchronization module is configured, after recalling data corresponding to the one or more stub files from the file server having the data according to the stub information, to migrate files of the recalled data to an external file server.

17. The new file server according to claim 11, wherein the new file server includes a hierarchical storage management module which is configured, upon receiving an I/O request for a file from one of the one or more host computers by the new file server, to:

determine whether the file of the I/O request is a stub file in the new file server;

if the file is not a stub file and the I/O request is not a write request, process the I/O request to access data in the new file server;

if the file is a stub file and the I/O request is not a write request, recall data corresponding to the stub file from the old file server according to the stub information to replace the one or more stub files; and

if the I/O request is a write request, write data of the write request to the new file server.

18. The new file server according to claim 17, wherein the hierarchical storage management module is configured to:

migrate data of the I/O request to an external file server.

19. The new file server according to claim 11, wherein the data synchronization module is configured to create one or more stub directories in the new file server, the one or more stub directories including stub information indicating location of data in one or more directories in the old file server;

the new file server further comprising;

a hierarchical storage management module which is configured, upon receiving an I/O request for a directory from one of the one or more host computers, to

determine whether the directory of the I/O request is a stub directory in the new file server;

if the directory is not a stub directory and the I/O request is not a write request, process the I/O request to access data in the new file server;

if the file is a stub directory and the I/O request is not a write request, recall data corresponding to the stub directory from the old file server according to the stub information to replace the one or more stub files; and

if the I/O request is a write request, write data of the write request to the new file server.

20. An information system comprising:

an old file server;

a new file server;

a backend network coupling the old file server and the new file server;

one or more host computers; and

a frontend network coupling the one or more host computers with the old and new file servers;

wherein the new file server is configured to

create stub files in the new file server, the stub files including stub information indicating location of data in the old file server, making it possible to switch I/O requests directed to the old file server to I/O requests directed to the new file server; and

upon receiving an I/O request by the new file server, check whether the new file server has any stub files and, if the new file server has one or more stub files, recall data corresponding to the one or more stub files from the old file server according to the stub information to replace the one or more stub files.