Remote access agent for caching in a SAN file system

• US 8,229,899 B2
• Filed: 02/16/2010
• Issued: 07/24/2012
• Est. Priority Date: 06/10/2004
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Anderson, Owen T., Gill, Binny S., Luan, Leo, Pereira, Manuel V. III, Riegel, Geoffrey A.
• Primary Examiner(s): PULLIAM, CHRISTYANN R
• Application Number:
  US12/706,233
• Publication Number:
  US 20100205156A1
• Time in Patent Office: 889 Days
• Field of Search: None
• US Class Current: 707/690
• CPC Class Codes: G06F 16/10 File systems; File servers

Abstract

A system and method is disclosed for maintaining, in a Storage Area Network (SAN), the consistency of a local copy of a remote file system sub-tree obtained from a remote source. Directory structure of the remote file system sub-tree is mapped to a remote container attached to the SAN and each remote object of the remote file system sub-tree is represented as a local object component of the remote container. Next, each of the local objects are labeled with attributes associated with the represented remote object, and metadata describing each of the local objects is stored in a metadata server. Also, a consistency policy is associated with each of the local objects in the remote container (wherein the policy defines conditions for checking freshness of said labeled attributes), and the local object components of remote container is updated in accordance with the consistency policy.

Claims

1. An article of manufacture comprising a non-transitory computer readable medium having computer readable program code embodied therewith to implement a method for maintaining consistency, in a Storage Area Network (SAN), of a local copy of a remote file system sub-tree obtained from a remote source;

said medium comprising;

a. computer readable program code mapping a directory structure of said remote file system sub-tree to a container;

said container attached to said SAN;

b. computer readable program code representing each remote object comprising said remote file system sub-tree as a local object component of said container;

c. computer readable program code labeling each said local object component with attributes associated with said represented remote object, said attributes comprising both content storage attributes and file attributes, each file attribute comprising at least a time stamp;

d. computer readable program code storing metadata comprising both said content storage attributes and said file attributes in a metadata server, said metadata server attached to said SAN and remotely located from said remote file system;

e. computer readable program code associating a consistency policy with each said local object component in said container;

said policy defining conditions for checking freshness of each said labeled object component that is labeled with said content storage attributes and file attributes; and

f. computer readable program code checking said metadata server for freshness of each labeled attribute according to at least an associated time stamp and updating each said local object component of said container in accordance with said consistency policy.

2. The article of manufacture of claim 1, wherein said local object components are hierarchically structured within said container in a manner corresponding to hierarchical structure of said remote objects comprising said remote file system sub-tree.

3. The article of manufacture of per claim 1, wherein said local and remote objects both represent either of:

a directory or a file.

4. The article of manufacture of claim 3, wherein when said local object component represents a directory, said local object component comprises at least a directory entry and directory attributes;

and when said local object component represents a file, said local object component comprises at least file content and file attributes.

5. The article of manufacture of claim 4, wherein said metadata is comprised of at least a local object component attribute and a consistency guarantee, said located object component comprising either a content storage attribute, when said local object component is a file, or at least one directory entry, when said local object component is a directory.

6. The article of manufacture of claim 5, wherein representing of said remote object as a local object component comprises:

when said local object component represents a file, storing said file content at a physical location specified by said content storage attribute; and

when said local object component represents a directory, populating said local object component with said directory entries.

7. The article of manufacture of claim 5, wherein said freshness checking comprises:

triggering a check of said attributes associated with each said local object component;

checking for the existence of said metadata defining a consistency guarantee for said local object component;

fetching from said remote source, attributes associated with said remote object represented by said local object component, based on results of said checking step;

creating a consistency guarantee for said local object component, based on results of said fetching step; and

merging said fetched attributes with said attributes associated with said local object component.

8. The article of manufacture of claim 7, wherein said check of attributes is triggered by either of:

synchronous or asynchronous methods.

9. The article of manufacture of claim 7, wherein said fetched attributes are accompanied by either of:

an explicit or an implicit consistency guarantee.

10. The article of manufacture of claim 9, wherein said implicit consistency guarantee exists for a pre-determined period of time.

11. The article of manufacture of claim 9, wherein said explicit consistency guarantee exists until notification is received from said remote source.

12. The article of manufacture of claim 7, wherein said freshness checking further comprises determining validity of said local object content by comparing said fetched attributes with said attributes associated with each said local object component, based on results of said checking step;

said comparison validating said local object component if said attributes associated with each said local object component matches attributes of said local content, else invalidating said local object content.

13. The article of manufacture of claim 7, wherein said local object component is updated with modifications made to a remote object imported from said remote source.

14. The article of manufacture of claim 7, wherein said remote object is updated with modifications made to a local object component exported to said remote source.

15. A system for updating, storing and accessing in a storage area network(SAN), a local copy of a remote file system sub-tree obtained from a remote source;

said system comprising;

a processor; and

computer storage, said computer storage storing;

computer readable program code executed by said processor to map a directory structure of said remote file system sub-tree to a container;

said container attached to said SAN;

computer readable program code executed by said processor to represent each remote object comprising said remote file system sub-tree as a local object component of said container;

computer readable program code executed by said processor to label each said local object component with attributes associated with said represented remote object, said attributes comprising both content storage attributes and file attributes, each file attribute comprising at least a time stamp;

computer readable program code executed by said processor to store metadata comprising both said content storage attributes and said file attributes in a metadata server, said metadata server attached to said SAN and remotely located from said remote file system;

computer readable program code executed by said processor to associate a consistency policy with each said local object component in said container;

said policy defining conditions for checking freshness of each said labeled object component that is labeled with said content storage attributes and file attributes; and

computer readable program code executed by said processor to check said metadata server for freshness of each labeled attribute according to at least an associated time stamp and update each said local object component of said container in accordance with said consistency policy.

16. The system of claim 15, wherein said local object components are hierarchically structured within said container in a manner corresponding to hierarchical structure of said remote objects comprising said remote file system sub-tree.

17. The system of claim 15, wherein said local and remote objects both represent either of:

a directory or a file.

18. The system of claim 17, wherein when said local object component represents a directory, said local object component comprises at least a directory entry and directory attributes;

and when said local object component represents a file, said local object component comprises at least file content and file attributes.

19. The system of claim 18, wherein said metadata is comprised of at least a local object component attribute and a consistency guarantee, said located object component comprising either a content storage attribute when said local object component is a file or at least one directory entry when said local object component is a directory.

20. The system of claim 19, wherein representing of said remote object as a local object component comprises:

when said local object component represents a file, storing said file content at a physical location specified by said content storage attribute; and

when said local object component represents a directory, populating said local object component with said directory entries.

21. The system of claim 19, wherein said freshness checking comprises:

triggering a check of said attributes associated with each said local object component;

checking for the existence of said metadata defining a consistency guarantee for said local object component;

fetching from said remote source, attributes associated with said remote object represented by said local object component, based on results of said checking step;

creating a consistency guarantee for said local object component, based on results of said fetching step; and

merging said fetched attributes with said attributes associated with said local object component.

22. The system of claim 21, wherein said check of attributes is triggered by either of:

synchronous or asynchronous methods.

23. The system of claim 21, wherein said fetched attributes are accompanied by either of:

an explicit or an implicit consistency guarantee.

24. The system of claim 23, wherein said implicit consistency guarantee exists for a pre-determined period of time.

25. The system of claim 24, wherein said explicit consistency guarantee exists until notification is received from said remote source.