Extended file system

• US 20050060316A1
• Filed: 04/07/2004
• Published: 03/17/2005
• Est. Priority Date: 03/25/1999
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Brown, Craig S., Gentile, Elizabeth J., Toussaint, Keith M., Pence, John B., Kamath, Vivek P., Lorimor, Thomas G., Firman, Thomas R., Shekaran, M. Chandra
• Granted Patent: US 7,542,999 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 16/10 File systems; File servers
• CPC Class Codes: Y10S 707/99933 Query processing, i.e. searching
• CPC Class Codes: Y10S 707/99952 Coherency, e.g. same view to multiple users
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

A method and system for transparently combining remote and local storage to provide an extended file system such as a virtual local drive for a computer system client/user, e.g., a user of a pocket sized personal computer or a cable set-top box. A client device may load file system object data, storing the directories and files remotely, and retrieving the files only when required. Via its local storage, the extended file system handles unreliable connections and delays. When a connection to an extended file system server is present, the extended file system provides automatic downloading of information that is not locally cached, and automatically uploading of information that has been modified on the client. Extended file system attributes are employed to determine the actual location of file system data, and a lightweight protocol is defined to download or upload remote data by low-level components that make the remote source transparent from the perspective of the application. The system scales to large networks as it employs the lightweight protocol and establishes a connection only to retrieve and submit data.

Claims

1. A computer-readable medium having computer-executable instructions, comprising:

receiving a request to access data, the data maintained on at least one of a local and remote source, the request originating from a first process that executes on a device that includes the local source;

determining by a second process that executes on the device whether the data is available from the local source; and

if the data is available from the local source, providing access to the data from the local source;

otherwise, retrieving at least some of the data from the remote source and providing access to the data.

2. The computer-readable medium of claim 1, wherein the first process is unaware as to where the data is maintained.

3. The computer-readable medium of claim 1, wherein the request includes no information as to whether the data is maintained at the local source or the remote source.

4. The computer-readable medium of claim 1, wherein the first process comprises an application.

5. The computer-readable medium of claim 1, wherein the first process comprises part of an operating system.

6. The computer-readable medium of claim 1, wherein the second process comprises a file system manager.

7. The computer-readable medium of claim 1, wherein determining whether the data is maintained at the local source comprises checking at least one attribute of a file system object associated with the data.

8. The computer-readable medium of claim 7, wherein the at least one attribute indicates that the data remain on the device and not be removed by a replacement algorithm that attempts to make room for more data on the device.

9. The computer-readable medium of claim 7, wherein the at least one attribute indicates that the data be always retrieved from the remote source when requested until the at least one attribute is changed to indicate otherwise.

10. The computer-readable medium of claim 1, further comprising:

modifying at least some of the data that is maintained at the local source; and

automatically updating the data on the remote source to synchronize the data on the remote source with the data on the local source.

11. A system for maintaining data, comprising:

a plurality of servers that are enlisted to provide data, wherein a server enlists to provide the data by performing acts, comprising;

sending an enlist primitive to notify the plurality of servers that the server seeks to participate in providing the data, and

receiving a response from at least one of the plurality of servers; and

a client that requests the data and maintains at least some of the data on a store local to the client and other than one provided by the servers.

12. The system of claim 11, wherein the server that is enlisting to provide the data performs further acts, comprising resending the enlist primitive to any of the plurality of servers that has not responded to the enlist primitive.

13. The system of claim 12, wherein resending the enlist primitive comprises transmitting the enlist primitive only to servers that have not responded.

14. The system of claim 11, wherein the client receives some of the data from at least one of the servers, marks the some of the data as local-always, and thereafter keeps the data in the store at least until the data is no longer marked as local-always.

15. The system of claim 11, wherein the client determines whether the client obtains the data from the plurality of servers or from the store local to the client.

16. The system of claim 11, wherein the client requests the data from the plurality of servers via a lightweight protocol that establishes a connection that is created just before the request is transmitted and the data returned and that is destroyed immediately thereafter.

17. The system of claim 11, wherein a request for the data from the client originates at the client.

18. A method for maintaining data, comprising in a file system maintained by a client, marking the data as synchronize-always or local-always;

if the data is marked as synchronize-always, obtaining the data from a server in response to a process that requests the data, the process executing on the client, the process originating the request; and

if the data is marked as local-always, obtaining the data from a store local to the client in response to the process requesting the data,

wherein the client determines where the data is obtained based on the marking of the data.

19. The method of claim 18, further comprising if the data is marked as synchronize always, transmitting any changes to the data to the server in response to a request that the data be changed, the request to change the data originating at the client.

20. The method of claim 18, further comprising if the data is marked as local-always, changing the data on the store local to the client in response to a request that the data be changed, the request to change the data originating at the client.