Method and apparatus for concurrent read-only access to filesystem

• US 7,904,492 B2
• Filed: 03/23/2006
• Issued: 03/08/2011
• Est. Priority Date: 03/23/2006
• Status: Active Grant

• Current Assignee: Network Appliance Incorporated (NetApp, Inc.)
• Original Assignee: Network Appliance Incorporated (NetApp, Inc.)
• Inventors: Sarma, Joydeep, Gole, Abhijeet
• Primary Examiner(s): Wong; Don
• Assistant Examiner(s): Nguyen; Kim T
• Application Number:
  US11/389,421
• Publication Number:
  US 20070226270A1
• Time in Patent Office: 1,811 Days
• Field of Search: 707/812, 707/822
• US Class Current: 707/812
• CPC Class Codes: G06F 16/128 Details of file system snapshots on the file-level, e.g. snapshot creation, administration, deletion use of snapshots for error detection or correction G06F11/14, G06F11/16
• CPC Class Codes: G06F 16/1767 Concurrency control, e.g. optimistic or pessimistic approaches
• CPC Class Codes: G06F 3/0601 Interfaces specially adapted for storage systems
• CPC Class Codes: G06F 3/0673 Single storage device

Abstract

A storage server obtains metadata to describe a filesystem, then processes the metadata to locate a data block and reads the data block from a remote storage subsystem. Apparatus and software implementing embodiments of the invention are also described and claimed.

Claims

1. A computerized method comprising:

obtaining, by a local storage server computer, metadata to describe hardware characteristics of a remote filesystem, the metadata stored in a local mass storage subsystem owned by the local storage server computer;

processing, by the local storage server computer, the metadata to locate a data block in the remote filesystem, the data block stored in a remote shared-access mass storage subsystem owned by a remote storage server computer, wherein the local storage server computer has read-only access to the remote shared-access mass storage subsystem; and

reading, by the local storage server computer, the data block from the remote shared-access mass storage subsystem using the metadata without requesting the data block from the remote storage server computer, wherein the local storage server computer reads the requested data block from the remote shared-access mass storage subsystem while the remote storage server computer accesses the remote shared-access mass storage subsystem.

2. The computerized method of claim 1 wherein the metadata describes a read-only persistent point-in-time image of the filesystem.

3. The computerized method of claim 1 wherein obtaining metadata comprises reading the metadata from the local mass storage subsystem.

4. The computerized method of claim 1 wherein processing the metadata yields a physical volume block number to locate the data block on the remote shared-access mass storage subsystem.

5. The computerized method of claim 1 wherein processing the metadata yields a virtual volume block number, the method further comprising:

translating the virtual volume block number to a physical volume block number.

6. The computerized method of claim 1, further comprising:

processing the data contained in the block to locate a second data block in the filesystem; and

reading the second block from the remote shared-access mass storage subsystem.

7. An apparatus comprising:

a local processor coupled to a local bus;

a local memory coupled to the local processor through the local bus;

a local storage interface coupled to the local bus;

a remote mass storage subsystem communicatively coupled to the local bus;

instructions executed by the local processor from the local memory to cause the local processor to read data, through the local storage interface, from the remote mass storage subsystem using hardware control information without requesting the data from a remote storage server, wherein the local processor reads the requested data from the remote mass storage subsystem while the remote storage server accesses the remote mass storage subsystem and wherein the remote mass storage subsystem is owned by the remote storage server and wherein the local processor has read-only access to the remote mass storage subsystem;

a local mass storage subsystem coupled to the local bus to store the hardware control information about a filesystem on the remote mass storage subsystem; and

filesystem parsing logic stored in the local memory and executed on the local processor to cause the local processor to locate a data block on the remote mass storage subsystem based on the hardware control information from the local mass storage subsystem and filesystem information from the remote mass storage subsystem.

8. The apparatus of claim 7, further comprising:

a communication interface to receive a request from a client;

protocol processing logic to interpret the request; and

control logic to read a data block corresponding to the request from the remote mass storage subsystem and return a content of the data block to the client.

9. The apparatus of claim 7 having read-only access to the remote mass storage subsystem.

10. The apparatus of claim 7 wherein a filesystem interpreted by the filesystem parsing logic is a read-only, persistent point-in-time image.

11. The apparatus of claim 7 wherein the filesystem parsing logic is to compute a physical volume block number based on the control information and filesystem information.

12. The apparatus of claim 7 wherein the filesystem parsing logic is to compute a virtual volume block number based on the control information and filesystem information, the apparatus further comprising:

translation logic to translate the virtual volume block number to a physical volume block number.

13. A computerized method comprising:

storing a remote filesystem on a remote shared-access mass storage subsystem owned by a remote storage server computer;

receiving, at the remote storage server computer, a first request for data in the remote filesystem;

processing, by the remote storage server computer, the first request;

returning, by the remote storage server computer, data corresponding to the first request;

receiving, at a local storage server computer, a second request for data in the remote filesystem;

parsing, by the local storage server computer, the remote filesystem to locate a virtual volume block number corresponding to a data block;

transmitting, by the local storage server computer, the virtual volume block number to the remote storage server computer;

receiving, by the local storage server computer, a physical volume block number corresponding to the virtual volume block number;

reading, by the local storage server computer, data from the remote shared-access mass storage subsystem at the physical volume block number without requesting the data from the remote storage server computer; and

returning, by the local storage server computer, data corresponding to the second request, wherein the local storage server computer processes the second request while the remote storage server computer processes the first request.

14. The computerized method of claim 13 wherein the filesystem is a read-only persistent point-in-time image (“

RPPI”

).

15. A computerized method comprising:

creating, by a remote computer, a read-only persistent point-in-time image (“

RPPI”

) of a filesystem stored in a container file on a mass storage subsystem;

receiving, by the remote computer, a virtual volume block number (“

VVBN”

) referencing a block of the container file from a local computer;

translating, by the remote computer, the VVBN to a physical volume block number (“

PVBN”

);

transmitting, by the remote computer, the PVBN to the local computer; and

reading, by the local computer, the block of the mass storage subsystem that corresponds to the PVBN without the local computer requesting the block from the remote computer, the reading occurring while the remote computer reads data from the mass storage subsystem.

16. The computerized method of claim 15, further comprising:

storing a copy of the filesystem on a backup medium.