Mechanism for exposing shadow copies in a networked environment

• US 7,730,033 B2
• Filed: 06/13/2003
• Issued: 06/01/2010
• Est. Priority Date: 06/13/2003
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Mohamed, Ahmed Hassan
• Primary Examiner(s): Rones; Charles
• Assistant Examiner(s): Adams; Charles D
• Application Number:
  US10/461,564
• Publication Number:
  US 20040254936A1
• Time in Patent Office: 2,545 Days
• Field of Search: 711/136, 711/162, 711/203, 711/216, 707/200, 707/204
• US Class Current: 707/649
• CPC Class Codes: G06F 16/10 File systems; File servers
• CPC Class Codes: G06F 2003/0697 device management, e.g. handlers, drivers, I/O schedulers
• CPC Class Codes: G06F 3/0601 Interfaces specially adapted for storage systems

Abstract

Described is a mechanism for exposing a volume shadow copy of a shared volume over a network to a remote client. A shared volume is accessed at a client computing system having a root. A volume shadow copy (or “snapshot”) of the volume is identified as a child resource of the shared volume. The child resource representing the snapshot may be hidden from ordinary view by default. To access the snapshot, a user may access the child resource as if it were an ordinary file or directory on the shared volume. Advantageously, the user need not mount a new volume representing the snapshot volume, but rather the user may directly access the snapshot.

Claims

1. A computer-readable storage medium having computer-executable instructions, a storage device comprising the computer-readable storage medium, the computer-executable instructions configured for associating a volume shadow copy with a current state of data stored on a shared volume, the instructions comprising:

sending a request from a user with access to a limited portion of a full data volume to a server;

wherein the full data volume is associated with a plurality of users, with each user associated with a set of permissions that define the limited portion of the full data volume the user may access;

wherein the shared volume comprises the limited portion of the full data volume that is made available to the user as a shared volume in response to access privileges associated with the user and the full data volume;

receiving a first file handle to a root of the shared volume;

obtaining a current directory structure, wherein the current directory structure includes a current state of data stored on the shared volume;

automatically creating a volume shadow copy of the shared volume for later recovery, wherein the volume shadow copy includes a volume shadow copy directory structure; and

wherein only the limited portion of the full data volume that is made available to the user as a share is obtained;

associating the volume shadow copy with the current directory structure, wherein the volume shadow copy directory structure is a child of the current directory structure, wherein the volume shadow copy directory structure is accessible from the current directory structure, and wherein the current directory structure and the volume shadow copy directory structure are part of the shared volume;

wherein a file within the shared volume is at a higher hierarchical level within the current directory structure than a corresponding file for the file that is within the volume shadow copy;

sending a request to the server for a second file handle to a snapshot file located in the volume shadow copy directory structure that is a child of the current directory structure;

receiving the second file handle from the server, wherein the second file handle includes a flag field that differentiates all files that are stored in both the current directory structure and the volume shadow copy directory structure such that the snapshot file included within the volume shadow copy of the shared volume and a standard file that are both located in the current directory structure are differentiated by an indication that the snapshot file is associated with the volume shadow copy, wherein the second file handle includes a share identifier identifying a root resource of the shared volume, the flag field indicates the share identifier refers to a snapshot share, and the flag field further indicates that the snapshot file referred to by the second file handle cannot be modified despite modification privileges associated with the snapshot file;

hiding the volume shadow copy so that the volume shadow copy is not visible in the current directory structure, wherein the name of the volume shadow copy is configured to prevent enumeration of the volume shadow copy directory structure;

receiving a request to display the volume shadow copy;

displaying the volume shadow copy in response to the request to display the volume shadow copy; and

accessing the volume shadow copy for the snapshot file.

2. The computer-readable storage medium of claim 1, wherein the current directory structure includes a directory tree structure.

3. The computer-readable storage medium of claim 1, wherein the shared volume is associated with a network file system protocol.

4. The computer-readable storage medium of claim 1, wherein the volume shadow copy is hidden by default.

5. The computer-readable storage medium of claim 1, wherein the volume shadow copy comprises a name uniquely distinguishing the volume shadow copy from other volume shadow copies of the shared volume.

6. The computer-readable storage medium of claim 5, wherein the name is based on a creation time of the volume shadow copy.

7. The computer-readable storage medium of claim 5, wherein the name is a virtual name.

8. The computer-readable storage medium of claim 1, wherein the current directory structure and the volume shadow copy directory structure include the same access requirements.

9. The computer-readable storage medium of claim 1, wherein access to the volume shadow copy directory structure uses access-control mechanisms based on permissions stored in association with the shared volume.

10. The computer-readable storage medium of claim 1, wherein access to the volume shadow copy is provided on a read-only basis.

11. The computer-readable storage medium of claim 1, wherein access to the volume shadow copy is provided on a read/write basis.

12. A system comprising a computer-readable storage medium encoded with a data structure, a storage device comprising the computer-readable storage medium, the data structure configured to accessing a volume shadow copy for a snapshot file, the system comprising:

sending a request from a user with access to a limited portion of a full data volume to a server;

wherein the full data volume is associated with a plurality of users, with each user associated with a set of permissions that define the limited portion of the full data volume the user may access;

wherein the shared volume comprises the limited portion of the full data volume that is made available to the user as a shared volume in response to access privileges associated with the user and the full data volume;

receiving a first file handle to a root of the shared volume;

obtaining a current directory structure, wherein the current directory structure includes a current state of data stored on the shared volume;

automatically creating a volume shadow copy of the shared volume for later recovery, wherein the volume shadow copy includes a volume shadow copy directory structure; and

wherein only the limited portion of the full data volume that is made available to the user as a share is obtained

associating the volume shadow copy with the current directory structure, wherein the volume shadow copy directory structure is a child of the current directory structure, wherein the volume shadow copy directory structure is accessible from the current directory structure, and wherein the current directory structure and the volume shadow copy directory structure are part of the shared volume;

wherein a file within the shared volume is at a higher hierarchical level within the current directory structure than a corresponding file for the file that is within the volume shadow copy;

sending a request to the server for a second file handle to the snapshot file located in the volume shadow copy directory structure that is a child of the current directory structure;

receiving the second file handle from the server, wherein the second file handle includes a flag field that differentiates all files that are stored in both the current directory structure and the volume shadow copy directory structure such that the snapshot file included within the volume shadow copy of the shared volume and a standard file that are both located in the current directory structure are differentiated by an indication that the snapshot file is associated with the volume shadow copy, wherein the second file handle includes a share identifier identifying a root resource of the shared volume, the flag field indicates the share identifier refers to a snapshot share, and the flag field further indicates that the snapshot file referred to by the second file handle cannot be modified despite modification privileges associated with the snapshot file;

hiding the volume shadow copy so that the volume shadow copy is not visible in the current directory structure, wherein the name of the volume shadow copy is configured to prevent enumeration of the volume shadow copy directory structure;

receiving a request to display the volume shadow copy;

displaying the volume shadow copy in response to the request to display the volume shadow copy; and

accessing the volume shadow copy for the snapshot file.

13. The system of claim 12, wherein the current directory structure and the volume shadow copy directory structure are maintained on the server and provided to a requesting client computer over a network.

14. The system of claim 13, wherein the server and the requesting client computer communicate using a network file system protocol.

15. The system of claim 12, wherein the volume shadow copy comprises a name based on a creation time of the volume shadow copy.

16. The system of claim 15, wherein the name is a hidden entry in the current directory structure by default.

17. A computer-implemented method for accessing a file over a distributed file system, the method comprising:

sending a request from a user with access to a limited portion of a full data volume to a server;

wherein the full data volume is associated with a plurality of users, with each user associated with a set of permissions that define the limited portion of the full data volume the user may access;

wherein the shared volume comprises the limited portion of the full data volume that is made available to the user as a shared volume in response to access privileges associated with the user and the full data volume;

receiving a first file handle to a root of the shared volume;

obtaining a current directory structure, wherein the current directory structure includes a current state of data stored on the shared volume;

automatically creating a volume shadow copy of the shared volume for later recovery, wherein the volume shadow copy includes a volume shadow copy directory structure; and

wherein only the limited portion of the full data volume that is made available to the user as a share is obtained

associating the volume shadow copy with the current directory structure, wherein the volume shadow copy directory structure is a child of the current directory structure, wherein the volume shadow copy directory structure is accessible from the current directory structure, and wherein the current directory structure and the volume shadow copy directory structure are part of the shared volume;

wherein a file within the shared volume is at a higher hierarchical level within the current directory structure than a corresponding file for the file that is within the volume shadow copy;

sending a request to the server for a second file handle to a snapshot file located in the volume shadow copy directory structure that is a child of the current directory structure;

receiving the second file handle from the server, wherein the second file handle includes a flag field that differentiates all files that are stored in both the current directory structure and the volume shadow copy directory structure such that the snapshot file included within the volume shadow copy of the shared volume and a standard file that are both located in the current directory structure are differentiated by an indication that the snapshot file is associated with the volume shadow copy, wherein the second file handle includes a share identifier identifying a root resource of the shared volume, the flag field indicates the share identifier refers to a snapshot share, and the flag field further indicates that the snapshot file referred to by the second file handle cannot be modified despite modification privileges associated with the snapshot file;

hiding the volume shadow copy so that the volume shadow copy is not visible in the current directory structure, wherein the name of the volume shadow copy is configured to prevent enumeration of the volume shadow copy directory structure;

receiving a request to display the volume shadow copy;

displaying the volume shadow copy in response to the request to display the volume shadow copy; and

accessing the volume shadow copy for the snapshot file.

18. The computer-implemented method of claim 17, further comprising evaluating access permissions associated with the requests to determine whether the permit access to the volume shadow copy.