Storage system and communications path control method for storage system

• US 20060075156A1
• Filed: 11/23/2004
• Published: 04/06/2006
• Est. Priority Date: 10/06/2004
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Nakamura, Hirofumi, Tanabe, Masayuki, Okaki, Takuya, Dohi, Hironori
• Granted Patent: US 7,451,341 B2
• Time in Patent Office: Days
• US Class Current: 710/17
• CPC Class Codes: G06F 11/201 between storage system components

Abstract

The present invention prompts path switching in accordance with the state of occurrence of intermittent failures, and prevents the responsiveness of a storage system from declining, or the like. Here, it is supposed, for example, that a host 1 is performing data communications with a storage device 2 by means of the path P1, and that an intermittent failure such as a communications time-out has occurred in path P1 on a number of occasions equal to or exceeding the prescribed threshold value. In this case, the controller 3 sends back a hardware error response in reply to an access from the host 1. Upon receiving a hardware error response from the storage device 2, the path control section 1B switches from the path P1 where the intermittent failure was detected (the original path) to a path P2 that is functioning normally (the target path), and then re-attempts the access command. In this way, it is possible to prompt the host 1 to switch the communications path in accordance with the state of occurrence of an intermittent failure, and therefore the responsiveness of the storage device 2 can be maintained.

Claims

1. A storage system comprising a plurality of host devices, and a storage device connectable respectively to these host devices by means of a plurality of communications paths;

comprising;

a communications status monitoring section for respectively monitoring the communications statuses between each of said host devices and said storage device;

a failure detecting section for detecting whether or not a prescribed minor failure has occurred, on the basis of at least said respective communications statuses detected by said communications status monitoring section;

a switching instruction section for outputting a switching request signal for requesting switching of the communications path, on the basis of the state of occurrence of said prescribed minor failure detected by said failure detecting section; and

a path control section for selecting the communications path to be used, on the basis of said switching request signal from said switching instruction section.

2. The storage system according to claim 1, wherein said host devices are able to share communications ports of said storage device, and said failure detecting section detects whether or not said prescribed minor failure has occurred with respect to communications ports that are shared by said host devices.

3. The storage system according to claim 1, wherein said prescribed minor failure is a temporary failure where there is a possibility of recovering communications.

4. The storage system according to claim 1, wherein said prescribed minor failures include at least a communications time-out status.

5. The storage system according to claim 1, wherein said failure detecting section judges that said prescribed minor failure has occurred in cases where a prescribed command has been issued by said host device, or cases where a prescribed status has been detected inside said storage device.

6. The storage system according to claim 1, wherein said failure detecting section judges that said prescribed minor failure has occurred, in cases where at least one of a processing abort command and a reset command has been issued by said host device, or cases where at least one of a communications time-out status and an abnormal status of the communications signal is detected in said storage device.

7. The storage system according to claim 1, wherein said switching instruction section outputs said switching request signal in response to access from said host device.

8. The storage system according to claim 1, wherein said switching instruction section outputs said switching request signal in response to a write access or read access from said host device, and does not output said switching request signal in response to a status enquiry access from said host device.

9. The storage system according to claim 1, wherein said switching request signal is a signal that only affects the host device related to said prescribed minor failure.

10. The storage system according to claim 1, wherein said switching request signal is a hardware error response.

11. The storage system according to claim 1, wherein said communications status monitoring section, said failure detecting section and said switching instruction section are provided within said storage device, and said path control section is provided within said host device.

12. The storage system according to claim 1, wherein said path control section is provided in a relay device disposed between said host device and said storage device.

13. The storage system according to claim 1, wherein said failure detecting section is provided in either said host device or said relay device.

14. The storage system according to claim 1, wherein threshold values are previously established respectively in association with each type of said prescribed minor failures, and said switching instruction section detects the number of occurrences respectively for each type of said prescribed minor failures and outputs said switching request signal, if the number of occurrences for any one prescribed minor failure of these types of prescribed minor failures has reached the corresponding threshold value.

15. The storage system according to claim 1, wherein, when detecting said switching request signal, said path control section judges whether or not there exists an available communications path, and when judging that an available communications path exists, then said path control section selects that available communications path.

16. The storage system according to claim 1, wherein, when detecting said switching request signal, then said path control section judges whether or not there exists an original communications path from which communications were switched on a previous occasion that said switching request signal was detected, and when judging that there exists an original communications path from which communications were switched due to detection of said switching request signal, then said path control section selects that original communications path.

17. A control method for communications paths in a storage system provided with a storage device connectable respectively to a plurality of host devices by means of a plurality of communications paths, in which the communications ports of said storage device can be shared by said respective host devices;

comprising;

a monitoring step of respectively monitoring the communications statuses between each of said host devices and said storage device;

a failure detecting step of detecting whether or not a prescribed minor failure has occurred, on the basis of said respective communications statuses thus detected;

a switching instruction step of outputting a switching request signal for requesting switching of the communications path, on the basis of the state of occurrence of said prescribed minor failure thus detected; and

a path selecting step of selecting the communications path to use, from among said plurality of communications paths, on the basis of said switching request signal.

18. The communications path control method for a storage system according to claim 17, wherein said switching instruction step comprises:

a judging step of judging whether or not an access to said storage device from a host device related to said prescribed minor failure has occurred; and

a step of outputting said switching request signal to said host device, if it is judged that said access has occurred.

19. The communications path control method for a storage system according to claim 17, wherein, when the access from said host device to said storage device is either a write access or a read access, the step of outputting said switching request signal outputs said switching request signal to the host device originating said access.

20. The communications path control method for a storage system according to claim 17, wherein a relay device for relaying communications between said respective host devices and said storage device is further provided, and said path selecting step selects said communications path to be used either within said host device, or within said relay device.