Method and system for a failover procedure with a storage system

• US 7,644,318 B2
• Filed: 11/09/2004
• Issued: 01/05/2010
• Est. Priority Date: 07/14/2004
• Status: Expired due to Fees

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Dicorpo, Jeffrey, Rauenzahn, Douglas W., Feather, Stanley S.
• Primary Examiner(s): Puente; Emerson C
• Application Number:
  US10/984,282
• Publication Number:
  US 20060015770A1
• Time in Patent Office: 1,883 Days
• Field of Search: 714/43, 714/56
• US Class Current: 714/43
• CPC Class Codes: G06F 11/2005 using redundant communication controllers
• CPC Class Codes: G06F 11/2007 using redundant communication media
• CPC Class Codes: G06F 11/201 between storage system components
• CPC Class Codes: G06F 11/2053 where persistent mass storage functionality or persistent mass storage control functionality is redundant error detection or correction in information storage based on relative movement between record carrier and transducer G11B20/18

Abstract

A method includes receiving a first command for accessing a tape storage system, the first command containing an indicator that the first command was issued as a result of a failover from a first path to the storage system to a second path to the tape storage system. The method further includes determining whether the first command is a repeat of a second command already received by the tape storage system. The first command is processed based on determining whether the first command is a repeat of the second command.

Claims

1. A tape storage system, comprising:

a tape storage medium;

a tape drive to access the tape storage medium; and

a controller to;

detect that a failover procedure from a failed path to a second path is occurring;

receive a first command over the second path, wherein the first command is to access content of the tape storage medium, and wherein the first command is a duplicate of a previously received second command; and

process the first command in the failover procedure without having to reposition the tape storage medium.

2. The tape storage system of claim 1, wherein the first command is a duplicate of the previously received second command sent over the failed path.

3. The tape storage system of claim 1, further comprising an interface to a storage area network, the failed path and second path being part of the storage area network.

4. The tape storage system of claim 1, wherein the controller is adapted to detect that the failover procedure is occurring based on receiving the first command containing a first predetermined indicator, the first predetermined indicator indicating that the failover procedure is occurring.

5. The tape storage system of claim 4, wherein the second command contains a second predetermined indicator, the second predetermined indicator indicating that the second command is a non-repeatable command.

6. The tape storage system of claim 5, wherein the second command is a write command, and wherein the controller is adapted to wait for all data for the second command to be received before submission of the second command to the tape drive.

7. The tape storage system of claim 5, wherein the controller processing the first command includes the controller discarding the first command and allowing the second command to be processed by the tape drive.

8. A tape storage system, comprising:

a tape storage medium;

a tape drive to access the tape storage medium;

a cache to store responses and data; and

a controller to;

detect that a failover procedure from a failed path to a second path is occurring;

receive a first command over the second path, wherein the first command is a duplicate of a previously received second command, wherein the controller is adapted to detect that the failover procedure is occurring based on receiving the first command containing a first predetermined indicator, the first predetermined indicator indicating that the failover procedure is occurring, wherein the second command contains a second predetermined indicator, the second predetermined indicator indicating that the second command is a non-repeatable command;

discard the first command;

process the second command without having to reposition the tape storage medium, wherein processing the second command includes;

if the second command is queued, sending the queued second command to the tape drive;

if the second command has been sent to the tape drive but has not yet completed, allowing the tape drive to complete processing; and

if the second command has completed, retrieving a response and any data for the completed second command from the cache.

9. A method of processing a command to access a tape storage system, comprising:

receiving a first command for accessing the tape storage system, the first command containing an indicator that the first command was issued as a result of a failover from a first path to the tape storage system to a second path to the tape storage system;

determining whether the first command is a repeat of a second command already received by the tape storage system;

discarding the first command in response to determining that the first command is a repeat of the second command; and

submitting the second command to a tape drive of the tape storage system in response to determining that the second command has been queued but has not yet been sent to the tape drive.

10. The method of claim 9, further comprising allowing the second command to be completed by the tape drive in response to determining that the second command has been sent to the tape drive but has not yet completed.

11. The method of claim 10, further comprising retrieving a response and any data from a cache in response to determining that the second command sent to the tape drive has completed.

12. The method of claim 9, further comprising receiving the second command, the second command having a second indicator to indicate that the second command is non-repeatable.

13. The method of claim 12, wherein the second command is a write command, the method further comprising waiting to submit the second command to a tape drive of the tape storage system until all write data for the second command has been received and cached.

14. Computer program code stored on at least one storage medium, the computer program code containing instructions that when executed cause a central processing unit (CPU) to:

detect that a first path to a tape storage system has failed;

in response to detecting that the first path has failed, send a first command over a second path to the tape storage system; and

add a first indicator to the first command, the first indicator to indicate to the tape storage system that the first command has been sent due to failover from the first path to the second path,

wherein the first command enables the tape storage system to perform a failover procedure without repositioning tape storage medium in the tape storage system.

15. The computer program code of claim 14, wherein the instructions when executed cause the CPU to:

send a second command over the first path to the tape storage system prior to failure of the first path; and

add a second indicator to the second command, the second indicator to indicate to the tape storage system that the second command is non-repeatable.

16. An article comprising at least one storage medium containing instructions that when executed cause a central processing unit (CPU) to:

receive a first command to access a tape storage system;

receive a second command containing a first indicator to indicate that failover from a first path to a second path has occurred as part of a failover procedure, wherein the second command is a duplicate of the first command;

process the second command in the failover procedure without having to reposition a tape storage medium in the tape storage system.

17. The article of claim 16, wherein receiving the first command comprises receiving the first command containing a second indicator, the second indicator indicating that the first command is a non-repeatable command.

18. The article of claim 17, wherein processing the second command includes discarding the second command and allowing the first command to be processed by the tape storage system.

19. A method of performing failover from a first path to a second path between a host and a tape storage system, comprising:

sending a first command over the first path to the tape storage system;

prior to completion of the first command, detecting that the first path has failed;

in response to detecting that the first path has failed, initiating a failover procedure, without user intervention, to identify the second path;

re-submitting the first command over the second path to the tape storage system, wherein the re-submitted first command contains an indicator to indicate that the re-submitted first command is associated with the failover procedure; and

processing, in the tape storage system, the re-submitted first command without re-positioning tape storage medium in the tape storage system.