Extended file system

• US 6,754,696 B1
• Filed: 03/24/2000
• Issued: 06/22/2004
• Est. Priority Date: 03/25/1999
• Status: Expired due to Term

• 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
• Primary Examiner(s): Follansbee, John
• Assistant Examiner(s): Hu, Jinsong
• Application Number:
  US09/535,058
• Time in Patent Office: 1,551 Days
• Field of Search: 709/203, 709/213, 709/218, 709/219, 707/3
• US Class Current: 709/213
• 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. In a computer system, a method of providing access to file system object data, comprising:

receiving a request to read data from a client application, the data residing on at least one of a local and a remote source, the client application being unaware of where the data resides, wherein the remote source includes a plurality of servers that are enlisted to provide the data;

determining where the data resides;

if the data does not reside on the local source, retrieving the data from the remote source and storing at least some of the data on the local source;

otherwise retrieving the data from the local source;

providing the data to the client application;

receiving a request from the client application to modify the data;

modifying at least some of the data that is stored on 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, 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 wants to participate in providing the data; and

receiving a response from at least one of the plurality of servers.

2. The method of claim 1, wherein the at least some of the data that is stored in the local source is stored in memory that serves as a file system.

3. The method of claim 2, wherein the memory serves as a ramdisk.

4. The method of claim 1, wherein the at least some of the data that is stored on the local source is stored in main memory, the main memory not serving as a file system.

5. The method of claim 4, wherein the data is part of an object that is marked as synchronize-always and wherein the data is always retrieved from the remote source when a request to read the data is received.

6. The method of claim 1, wherein the data is part of an object marked as local-always, wherein after the data is retrieved from the remote source, the data remains on the local source and is not removed via a least-recently-used algorithm employed to make room on the local source for other data.

7. The method of claim 1, wherein the data is transmitted via a connection that is created just before the data is transmitted and that is destroyed immediately thereafter.

8. The method of claim 1 wherein determining where the data resides comprises accessing attributes of an object associated with the data.

9. The method of claim 1, 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.

10. The method of claim 9, wherein resending the enlist primitive is transmitted directly to servers that have not responded.

11. The method of claim 1, wherein the enlist primitive is sent via a broadcast.