SNAPSHOT MECHANISM IN A DATA PROCESSING SYSTEM AND METHOD AND APPARATUS THEREOF

Abstract

A snapshot mechanism of a data processing system is provided herein. The snapshot mechanism includes providing a snapshot storage unit for storing the data created when snapshotting the target storage units and generating a plurality of snapshot images accordingly. Two different types of address tables in the snapshot image are used for corresponding to the storage units of the snapshot storage unit and the target storage units. The status of the target storage units can be recovered to the status at a predetermined time ago according to the snapshot images. The two types of address tables are respectively used for storing the data created by the data processing system and history data so as to prevent the data stored in the target storage units to be overwritten.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

FIG. 1 is a diagram illustrating a conventional Copy-on-Write (CoW) technology.

FIG. 2 is a diagram illustrating another conventional CoW technology.

FIG. 3 is a diagram illustrating the structure of a snapshot technology according to an embodiment of the present invention.

FIG. 4 is a diagram illustrating the structure of a snapshot technology and the composition of a snapshot module according to an embodiment of the present invention.

FIG. 5A is a diagram illustrating the composition of a snapshot image, including the correspondence between a primary bitmap table and target volumes and the correspondence between a removed history data CoW bitmap table and a snapshot volume, according to an embodiment of the present invention.

FIG. 5B is a diagram illustrating the composition of a primary bitmap table and a Removed history data CoW bitmap table according to an embodiment of the present invention.

FIG. 6 is a diagram illustrating the access correspondence between snapshot images and target volumes and snapshot volume according to an embodiment of the present invention.

FIG. 7 is a flowchart illustrating the CoW procedure according to an embodiment of the present invention.

FIG. 8 is an access flowchart illustrating the method of reading history data directly from a snapshot image without performing recovery according to an embodiment of the present invention.

FIG. 9 is a flowchart illustrating that the target volumes can be restored to the status at the time of making any snapshot image when performing recovery status mechanism according to an embodiment of the present invention.

Claims

1. A snapshot mechanism of a data processing system, comprising: providing a snapshot storage unit, used for storing the data created by snapshotting a plurality of target storage units and creating a plurality of snapshot images according to created data;using a first address table and a second address table in a snapshot image respectively corresponding to a plurality of storage units of the snapshot storage unit and the target storage units; andrestoring the status of the target storage units to the status of a predetermined time ago according to the snapshot images.

2. The snapshot mechanism as claimed in claim 1, wherein the target storage units corresponding to the first address table are used for storing the data generated by the data processing system, and the snapshot storage unit corresponding to the second address table is used for storing a plurality of history data so as to avoid overwriting the data stored in the target storage units.

3. The snapshot mechanism as claimed in claim 2, wherein the first address table includes a list of addresses corresponding to the storage units of the target storage units, wherein the addresses of the storage units are mapped one-to-one to the target storage units.

4. The snapshot mechanism as claimed in claim 2, wherein the second address table includes a list of addresses corresponding to the storage units of the snapshot storage unit, wherein the address lengths of the storage units are mapped one-to-one to the target storage units.

5. The snapshot mechanism as claimed in claim 1, wherein the sizes of the first address table and the second address table in the snapshot image are the same.

6. The snapshot mechanism as claimed in claim 1 further comprising a snapshot module used for managing the snapshot images and controlling the storage units of the snapshot storage unit.

7. The snapshot mechanism as claimed in claim 6, wherein the snapshot module is a software module, which can be used in the data processing system.

8. The snapshot mechanism as claimed in claim 6, wherein the snapshot module comprises: a snapshot storage unit management unit, used for writing into the storage units of the snapshot storage unit and reporting the available storage units in the snapshot storage unit;a snapshot image storage unit, used for storing the created snapshot images;a snapshot administration unit, receiving the data transmitted from the target storage units, determining whether to transmit the data to the snapshot storage management unit to store the data into the snapshot storage unit after comparing the data with the snapshot images stored in the snapshot image storage unit, updating the snapshot image corresponding to the data with the address of the stored data.

9. The snapshot mechanism as claimed in claim 1 further comprising that while a write request being received, checking whether the snapshot image of the target storage unit corresponding to the write request having been created; andchecking that whether the addresses of the storage units in the second address table corresponding to the addresses of the storage units of the read request having been updated, if any address in the second address table having been not updated, performing a Copy-on-Write (CoW) procedure to store the data in the storage units corresponding to the write request into the snapshot storage unit, and updating the addresses of the storage units which having not been updated in the second address table.

10. The snapshot mechanism as claimed in claim 1 further comprising that while a read request for preview being received, selecting one of the created snapshot images; andobtaining an original address corresponding to the read request from the first address table, obtaining the address of a history data corresponding to the read request from the second address table, capturing data from the storage unit of the target storage unit corresponding to the original address if the address of the history data having not been updated, capturing data from the storage unit of the snapshot storage unit corresponding to the address of the history data if the address of the history data having been updated.

11. The snapshot mechanism as claimed in claim 1 further comprising that while a recovery request being received, selecting one of the created snapshot images;obtaining an original address corresponding to the recovery request from the first address table, obtaining the address of a history data corresponding to the recovery request from the second address table;obtaining the history data from the snapshot storage unit according to the address of the history data; andwriting the history data into the storage unit of the target storage unit corresponding to the original address.

12. The snapshot mechanism as claimed in claim 11, wherein the created snapshot images are selected according to the snapshot images created at the predetermined time of the target storage unit to be recovered.

13. The snapshot mechanism as claimed in claim 1, wherein the storage unit comprises at least a sector, a track, block, a cluster, a disk, a tape(song) or a volume.

14. A snapshot method of a data processing system, applicable to a snapshot storage unit and a plurality of target storage units, the snapshot method comprising: creating a plurality of snapshot images sequentially, storing the created snapshot images into the snapshot storage unit, wherein each of the snapshot images has a first address table and a second address table respectively corresponding to a plurality of storage units of the snapshot storage unit and the target storage units;selecting the snapshot image of the target storage unit corresponding to the recovery request according to an appointed time and a recovery request;obtaining an original address corresponding to the recovery request from the first address table, obtaining the address of a history data corresponding to the recovery request from the second address table;obtaining the history data from the snapshot storage unit according to the address of the history data; andwriting the history data into the storage unit of the target storage unit corresponding to the original address.

15. The snapshot method as claimed in claim 14, wherein the first address table includes a list of addresses corresponding to the storage units of the target storage units, wherein the addresses of the storage units are mapped one-to-one to the target storage units.

16. The snapshot method as claimed in claim 14, wherein the second address table includes a list of addresses corresponding to the storage units of the snapshot storage unit, wherein the address lengths of the storage units are mapped one-to-one to the target storage units.

17. The snapshot method as claimed in claim 14, wherein the sizes of the first address table and the second address table in the snapshot image are the same.

18. A snapshot method of a data processing system, applicable to a snapshot storage unit and a plurality of target storage units, the snapshot method comprising: creating a plurality of snapshot images sequentially, storing the created snapshot images into the snapshot storage unit, wherein each of the snapshot image includes a first address table and a second address table respectively corresponding to a plurality of storage units of the snapshot storage unit and the target storage units;selecting the snapshot image of the target storage unit corresponding to the read request according to an appointed time and a read request for preview;obtaining an original address corresponding to the recovery request from the first address table, obtaining the address of a history data corresponding to the recovery request from the second address table; andcapturing data from the storage unit of the target storage unit corresponding to the original address if the address of the history data having not been updated, capturing data from the storage unit of the snapshot storage unit corresponding to the address of the history data if the address of the history data having been updated.

19. The snapshot method as claimed in claim 18, wherein the first address table includes a list of addresses corresponding to the storage units of the target storage units, wherein the addresses of the storage units are mapped one-to-one to the target storage units.

20. The snapshot method as claimed in claim 18, wherein the second address table includes a list of addresses corresponding to the storage units of the snapshot storage unit, wherein the address lengths of the storage units are mapped one-to-one to the target storage units.

21. The snapshot method as claimed in claim 8, wherein the sizes of the first address table and the second address table in the snapshot image are the same.

22. A snapshot data processing apparatus, comprising: a snapshot storage unit, used for storing the data created when snapshotting a plurality of target storage units and generating a plurality of snapshot images accordingly, wherein each of the snapshot image includes a first address table and a second address table respectively corresponding to a plurality of storage units of the snapshot storage unit and the target storage units; anda snapshot module, used for managing the snapshot images and controlling the storage units of the snapshot storage unit, restoring the status of the target storage units to the status of a predetermined time ago according to the snapshot images.

23. The snapshot data processing apparatus as claimed in claim 22, wherein the snapshot module comprises: a snapshot storage unit management unit, used for writing into the storage units of the snapshot storage unit and reporting the available storage units in the snapshot storage unit;a snapshot image storage unit, used for storing the created snapshot images; anda snapshot administration unit, receiving the data transmitted from the target storage units, determining whether to transmit the data to the snapshot storage management unit to store the data into the snapshot storage unit after comparing the data with the snapshot images stored in the snapshot image storage unit, updating the snapshot image corresponding to the data with the address of the stored data.

24. The snapshot data processing apparatus as claimed in claim 22, wherein the target storage units corresponding to the first address table are used for storing the data created by the data processing system, and the snapshot storage unit corresponding to the second address table is used for storing a plurality of history data so as to avoid overwriting the data stored in the target storage units.

25. The snapshot data processing apparatus as claimed in claim 24, wherein the first address table includes a list of addresses corresponding to the storage units of the target storage units, wherein the addresses of the storage units are mapped one-to-one to the target storage units.

26. The snapshot data processing apparatus as claimed in claim 24, wherein the second address table includes a list of addresses corresponding to the storage units of the snapshot storage unit, wherein the address lengths of the storage units are mapped one-to-one to the target storage units.