Storage system and control method for the same

• US 20070245114A1
• Filed: 09/28/2006
• Published: 10/18/2007
• Est. Priority Date: 04/18/2006
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Kakui, Kentaro, Achiwa, Kyosuke
• Granted Patent: US 7,680,984 B2
• Time in Patent Office: Days
• US Class Current: 711/170
• CPC Class Codes: G06F 3/0608 Saving storage space on storage systems
• CPC Class Codes: G06F 3/0613 in relation to throughput
• CPC Class Codes: G06F 3/0631 by allocating resources to storage systems
• CPC Class Codes: G06F 3/0665 at area level, e.g. provisioning of virtual or logical volumes
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]

Abstract

An object of the present invention is to improve the usage efficiency of a storage extent in a storage system using the AOU technique. A controller in the storage system allocates a storage extent in an actual volume to an extent in a virtual volume accessed by a host computer, detects any decrease in necessity for maintaining that allocation, and cancels the allocation of the storage extent in the actual volume to the extent in the virtual volume based on the detection result.

Claims

1. A storage system having a storage device and a controller that controls data input and output to/from the storage device in response to a request from a host computer connected to the storage system via a communication path, the storage system comprising:

a virtual volume accessed by the host computer; and

an actual volume including at least one storage extent in the storage device,

wherein the host computer accesses the storage extent in the actual volume via the virtual volume, as the actual volume is allocated to the virtual volume, and

wherein the controller allocates a storage extent in the actual volume to an extent in the virtual volume accessed by the host computer in response to the access from the host computer to the virtual volume, detects any decrease in necessity for maintaining that allocation, and cancels the allocation of the storage extent in the actual volume to the extent in the virtual volume based on the detection result.

2. The storage system according to claim 1 comprising a first virtual volume and a second virtual volume that are in a copy pair relationship, wherein the controller detects the cancellation of the copy pair relationship and cancels the allocation of the storage extent to the virtual volume that is a copy destination.

3. The storage system according to claim 1 comprising a first virtual volume and a second virtual volume that are in a copy pair relationship, wherein the controller cancels the allocation of the storage extent to the volume that is a copy destination, after copy between those volumes has finished and data in the copy destination volume has been backed up to an external medium.

4. The storage system according to claim 1 comprising control memory for storing control information used for determining the state of an access from the host computer, wherein the controller executes the cancellation according to the control information content.

5. The storage system according to claim 4, wherein the control information is information indicating whether a storage extent has actually been accessed by the host computer or is expected to be accessed later by the host computer.

6. The storage system according to claim 4, wherein the controller regularly scans the control information for a storage extent in the actual volume and executes cancellation based on the scan results.

7. The storage system according to claim 1, wherein the controller executes the cancellation based on the result of executing an application program in the host computer.

8. The storage system according to claim 1, wherein, on the grounds that an application program in the host computer deletes data, the controller cancels the allocation of the storage extent in the actual volume related to the deleted data.

9. The storage system according to claim 1, wherein the controller monitors access commands from the host computer to the virtual volume and executes cancellation based on the access commands.

14. The storage system according to claim 1, wherein the controller calculates the proportion of the storage extent allocated to the virtual volume in the storage extent in the actual volume and executes cancellation if the calculated proportion is a certain value or more.

15. The storage system according to claim 1, wherein the controller deletes data in the storage extent in the actual volume that has been subjected to the cancellation.

10. A storage system having a storage device and a controller, that controls data input and output to/from the storage device in response to a request from a host computer connected to the storage device via a communication path, the storage system comprising:

a virtual volume accessed by the host computer; and

an actual volume including at least one storage extent in the storage device,

wherein the host computer accesses the storage extent in the actual volume via the virtual volume, as the actual volume is allocated to the virtual volume, and

wherein the controller allocates a storage extent in the actual volume to an extent in the virtual volume accessed by the host computer in response to the access from the host computer to the virtual volume, predicts extents in the virtual volume that will be subsequently accessed by the host computer, and allocates storage extents in the actual volume to the predicted extents.

11. The storage system according to claim 10, wherein the controller cancels the allocation of the storage extent in the actual volume to the predicted extent based on the state of an access from the host computer to the predicted extent.

12. The storage system according to claim 10 comprising control information about an extent in the virtual volume for distinguishing between an extent that has been accessed by the host computer and the predicted extent, wherein the controller executes cancellation based on the control information.

13. The storage system according to claim 12, wherein the controller periodically refers to the control information and executes cancellation based on the same.

16. A control method in a storage system having a storage device and a controller that controls data input and output to/from the storage device in response to a request from a host computer connected to the storage system via a communication path,

the storage system comprising a virtual volume accessed by the host computer and an actual volume including at least one storage extent in the storage device, the storage system being one where the host computer accesses a storage extent in the actual volume via the virtual volume, as the actual volume is allocated to the virtual volume, and

the control method comprising the steps of:

the controller allocating a storage extent in the actual volume to an extent in the virtual volume accessed by the host computer in response to an access from the host computer to the virtual volume; and

the controller cancelling the allocation of the storage extent in the actual volume to the extent in the virtual volume in which the necessity of maintaining the allocation has decreased.