STORAGE SYSTEM AND CONTROL METHOD FOR THE SAME

• US 20100146207A1
• Filed: 02/11/2010
• Published: 06/10/2010
• 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 7,949,828 B2
• Time in Patent Office: Days
• US Class Current: 711/114
• 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 an access request from a host computer connected to the storage system via a communication path, the storage system comprising:

an actual volume including a plurality of storage extents in the storage device, and

a virtual volume accessed by the host computer and including a plurality of virtual extents, at least one of the plurality of storage extents being allocated to at least one of the plurality of virtual extents, and at least one storage extent of the plurality of storage extents not being allocated to at least one of the plurality of virtual extents,

wherein in response to an access request to a first virtual volume from the host computer, the controller allocates a first storage extent of the plurality of storage extents to the first virtual extent of the plurality of the virtual extents and tends to allocates a second storage extent of the plurality of storage extents to a second virtual extent of the plurality of the virtual extents, if no storage extent in the storage device has been allocated to the first virtual extent and the second virtual extent,

wherein the second virtual extent is expected to be accessed by a subsequent access request after said access request to a first virtual volume.

2. A storage system according to claim 1,

wherein an address of the second virtual extent is immediately after an address of the first virtual volume.

3. A storage system according to claim 1,

wherein if the second virtual extent is not accessed by an access request from the host computer after the allocating the second storage extent to the virtual extent the controller to, the controller cancels the allocation between the second virtual extent and the second storage extent.

4. A storage system according to claim 3,

wherein the controller cancels the allocation between the second virtual extent and the second storage extent when the number of the storage extents, which have not been allocated to any of the plurality of virtual extents in the virtual volume, is lower than predetermined threshold.

5. A storage system according to claim 1,

wherein the controller writes zero data to said first storage extent when the controller cancel allocation between the first virtual extent and the first storage extent.

6. A storage system according to claim 1,

wherein, if the number of the storage extents, which have not been allocated to any of the plurality of virtual extents in the virtual volume, is not enough to allocate the first storage extent to the first virtual extent, the controller sends an error message to the host computer in response to the access command to the first virtual extent,

if the number of the storage extents, which have not been allocated to any of the plurality of virtual extents in the virtual volume, is enough to allocate the first storage extent to the first virtual extent, but not enough to allocate the second storage extent to the second virtual extent, the controller does not send an error message to the host computer in response to the access command to the first virtual extent.

7. A storage method for use with a storage device and a controller that controls data input and output to/from the storage device in response to an access request from a host computer connected to the storage system via a communication path, comprising:

accessing, by the host computer, a virtual volume including a plurality of virtual extents,

allocating, by the host computer, at least one of a plurality of storage extents of an actual volume in the storage device to at least one of the plurality of virtual extents, but with at least one of the storage extents of the plurality of storage extents not being allocated to at least one of the plurality of virtual extents;

allocating, by the controller, in response to an access request to a first virtual volume from the host computer, a first storage extent of the plurality of storage extents to a first virtual extent of the plurality of the virtual extents;

allocating, by the controller, a second storage extent of the plurality of storage extents to a second virtual extent of the plurality of the virtual extents, if no storage extent in the storage device has been allocated to the first virtual extent and the second virtual extent;

wherein the controller is configured electronically to receive a subsequent access request for the second virtual extent after said access request to a first virtual volume.

8. A storage method according to claim 7,

wherein an address of the second virtual extent is immediately after an address of the first virtual volume.

9. A storage method according to claim 7,

cancelling electronically, by the controller, the allocation between the second virtual extent and the second storage extent if the second virtual extent is not accessed by an access request from the host computer after the allocating the second storage extent to the virtual extent.

10. A storage method according to claim 9,

cancelling electronically, by the controller, the allocation between the second virtual extent and the second storage extent when the number of the storage extents which have not been allocated to any of the plurality of virtual extents in the virtual volume, is lower than predetermined threshold.

11. A storage method according to claim 9,

writing electronically, by the controller, zero data to said first storage extent when the controller cancel allocation between the first virtual extent and the first storage extent.

12. A storage method according to claim 7,

sending electronically, by the controller, an error message to the host computer in response to the access command to the first virtual extent, if the number of the storage extents, which have not been allocated to any of the plurality of virtual extents in the virtual volume, is not enough to allocate the first storage extent to the first virtual extent, and

if the number of the storage extents, which have not been allocated to any of the plurality of virtual extents in the virtual volume, is enough to allocate the first storage extent to the first virtual extent, but not enough to allocate the second storage extent to the second virtual extent, not sending, by the controller, an error message to the host computer in response to the access command to the first virtual extent.