Method and system for client-side caching

• US 20040236777A1
• Filed: 06/30/2004
• Published: 11/25/2004
• Est. Priority Date: 08/14/1998
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Raman, Balan Sethu, Pardikar, Shishir, Corrington, Robert E., Linn, Joseph L.
• Granted Patent: US 7,089,284 B2
• Time in Patent Office: Days
• US Class Current: 707/100
• CPC Class Codes: G06F 16/172 Caching, prefetching or hoarding of files
• CPC Class Codes: G06F 16/182 Distributed file systems
• CPC Class Codes: G06F 16/9574 of access to content, e.g. by caching
• CPC Class Codes: G06F 21/6218 to a system of files or objects, e.g. local or distributed file system or database
• CPC Class Codes: G06F 2221/2141 Access rights, e.g. capability lists, access control lists, access tables, access matrices

Abstract

An improved method and system for client-side caching that transparently caches suitable network files for offline use. A cache mechanism in a network redirector transparently intercepts requests to access server files, and if the requested file is locally cached, satisfies the request from the cache when possible. Otherwise the cache mechanism creates a local cache file and satisfies the request from the server, and also fills in a sparse cached file as reads for data in ranges that are missing in the cached file are requested and received from the server. A background process also fills in local files that are sparse, using the existing handle of already open server files, or opening, reading from and closing other server files. Security is also provided by maintaining security information received from the server for files that are in the cache, and using that security information to determine access to the file when offline.

Claims

1. In a computing environment, a method, comprising:

maintaining a file cache at a local computing device;

receiving, at a redirector of the local computing device, a file system-directed write request from a program to write data to a server file;

evaluating an online or offline state of the local computing device and a property set of the server file that is accessible to the local computing device to determine whether to write data to the cache, to the server file, or to both the cache and the server file; and

satisfying the write request by writing data to the cache, to the server file, or to both the cache and the server file based on the online or offline state and property set evaluation.

2. The method of claim 1 wherein the property set associated with the server file indicates that no caching is to be performed for the server file, and wherein satisfying the write request comprises writing data to the to the server file.

3. The method of claim 1 wherein the state is offline and the property set associated with the server file indicates that caching is allowed, and wherein satisfying the write request comprises writing data to the to the cache.

4. The method of claim 1 wherein the property set associated with the server file indicates that caching is to be manually decided by the user, and wherein satisfying the write request comprises determining from user instructions whether the file can be cached, and if so, writing data to the to the cache.

5. The method of claim 1 further comprising, receiving security information corresponding to the server file at the computing device, and maintaining the security data in association with a cached copy of the server file.

6. The method of claim 1 further comprising, maintaining a setting on the local computing device that indicates that a cached copy of the server file should not be removed from the cache based on a cache quota.

7. A computer-readable medium having computer-executable instructions, which when executed, perform the method of claim 1.

8. A method of synchronizing file data on a client computer system and a network server computer system, comprising:

receiving at the client computer system a file system write request to write data to a network server file;

determining whether the write request is directed towards a network server file that has an associated policy setting indicating that the network server file has a locally cached copy,

and if not;

writing the data to the network server file;

and if so;

writing the data to a corresponding local file in a local cache, and if the client computer system is not connected to the network server, synchronizing the data written to the local file with the network server file at a time when the client computer system is connected to the network server.

9. The method of claim 8 wherein the policy settings indicate that the network server file has a locally cached copy, and wherein the client computer system is connected to the network server, and further comprising, receiving a file system read request to read data from a network server file, accessing the locally cached copy, determining whether data present in the locally cached copy is missing with respect to the read request, and if the data in the local file is missing with respect to the read request, accessing the network server file to obtain at least one portion of missing data to return a set of data that satisfies the read request.

10. The method of claim 9 wherein the set of data includes some data from the locally cached copy and some data from the network server file.

11. The method of claim 10 further comprising writing the at least one set of missing data accessed via the network server file to the locally cached copy.

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

receiving a file system read request to read a range of data from a network server file, the range capable of starting at an arbitrary offset within the file data;

in response to the read request, accessing a local file that corresponds to the server file and determining whether any data within the range of data requested from the server file is missing in the local file with respect to the read request; and

if any data in the local file is missing with respect to the read request, accessing the network server file to obtain at least one set of missing data to return the requested range of data in its entirety in response to the read request.

13. The method of claim 12 further comprising filling at least part of the local file with data from the server file when the local file is sparse.

14. The method of claim 13 wherein the local file is sparse, and further comprising, filling at least part of the local file via a background process.

15. The method of claim 14 wherein the background process determines that the local file is already open, obtains a file handle of the open file, and issues a read request via the file handle of the open file.

16. A computer-readable medium having computer-executable instructions for performing the method of claim 15.

17. A computer-readable medium having computer-executable components for caching files and accessing network files, comprising:

a redirector component; and

a caching component configured to detect a file system-directed request for accessing a server file of a network server and to determine if a local file corresponding to the server file is already in a local cache; and

if the local file is in the local cache, to open the local file for access, and

if the local file is not in the local cache, to open the server file, and to analyze at least one policy setting associated with the server file that indicates whether a local file in the local cache may be created to correspond to the server file, and if so, creating the file.

18. The computer-readable medium of claim 17 wherein the caching component is part of the redirector component.

19. The computer-readable medium of claim 17 wherein the caching component further includes instructions for receiving security information corresponding to the server file from the network server, and for maintaining security data in association with the local file corresponding to the security information.

20. The computer-readable medium of claim 19 wherein the caching component further includes instructions for receiving a request to access a cached file, and for using the security information associated with the cached file to determine access to the file.