Resynchronizing to a first storage system after a failover to a second storage system mirroring the first storage system

Patent metadata

Field	Value
Publication number	US-10936447-B2
Application number	US-201816128435-A
Country	US
Kind code	B2
Filing date	Sep 11, 2018
Priority date	May 5, 2015
Publication date	Mar 2, 2021
Grant date	Mar 2, 2021

Abstract

Provided are a computer program product, system, and method for performing a failover between a first storage system and a second storage system. Data is synchronized between the first storage system and the second storage system. A failover is performed from the first storage system to the second storage system in response to a failover event at the first storage system while synchronizing the data. A determination is made that a first storage unit of the first storage system is inoperable and that that a second storage unit of the first storage system is operable in response to the failover event. In response to determining that the second storage unit is operable, a resynchronization is initiated to copy updates to a second storage unit of the second storage system mirroring the second storage unit of the first storage system to the second storage unit of the first storage system.

First claim

What is claimed is:

1. A computer program product for performing a failover between a first storage system and a second storage system, wherein the computer program product comprises a computer readable storage medium having program instructions embodied therewith, the program instructions executable by a processor to cause operations, the operations comprising:
synchronizing data between the first storage system and the second storage system;
performing a failover from the first storage system to the second storage system in response to a failover event at the first storage system while synchronizing the data, wherein Input/Output (I/O) requests to the first storage system are redirected to the second storage system as part of the failover, wherein the second storage system includes a first storage unit and a second storage unit that correspond to a first storage unit and a second storage unit in the first storage system, respectively; and
in response to determining during the failover that the second storage unit in the first storage system is operable while the first storage unit in the first storage system is inoperable, initiating a resynchronization to copy updates from the second storage unit of the second storage system, mirroring the second storage unit of the first storage system, to the second storage unit of the first storage system, while I/O requests are being redirected to the second storage system.

2. The computer program product of claim 1 , wherein the synchronization of the data between the first storage system and the second storage system are performed in synchronous copy mode and wherein the copying of the updates during the resynchronization while I/O requests are being redirected to the second storage system are performed in asynchronous copy mode.

3. The computer program product of claim 1 ,
wherein the determining that the first storage unit is inoperable comprises:
initiating a point-in-time copy of the first storage unit of the first storage system; and
determining that the point-in-time copy of the first storage unit failed, wherein the first storage unit is determined to be inoperable in response to determining that the point-in-time copy of the first storage unit failed;

wherein the determining that the second storage unit is operable comprising:
initiating a point-in-time copy of the second storage unit of the first storage system; and
determining that the point-in-time copy of the second storage unit succeeded, wherein the second storage unit is determined to be operable in response to determining that the point-in-time copy of the second storage unit succeeded.

4. The computer program product of claim 3 , wherein the operations further comprise:
initiating a soft fence state for the first storage system to prevent I/O access to the first and the second storage units at the first storage system in response to the failover event, wherein point-in-time copies are initiated with a command having a parameter to allow point-in-time copy operations to proceed during the soft fence state of the first storage system.

5. The computer program product of claim 3 , wherein the first storage units comprise first volumes of the first and second storage systems and wherein the second storage units comprise second volumes of the first and second storage systems.

6. The computer program product of claim 1 , wherein the resynchronization comprises a first resynchronization, wherein the operations further comprise:
issuing a health query to the first storage system to determine whether the first storage system is fully operable, wherein both the first and second storage units of the first storage system are operable when the first storage system is fully operable; and
initiating a second resynchronization to copy updates to the first storage unit of the second storage system to the first storage unit of the first storage system in response to determining that the response to the health query indicates the first storage system is fully operable.

7. The computer program product of claim 6 , wherein the first storage units comprise first volumes of the first and second storage systems and wherein the second storage units comprise second volumes of the first and second storage systems, wherein the first volume determined to be inoperable includes a subset of tracks experiencing data loss, wherein the second resynchronization further performs in response to the health query indicating that the first storage system is fully operable:
copying a subset of tracks in the first volume of the second storage system to a corresponding subset of tracks in the first volume in the first storage system, wherein tracks in the first volume in the first storage system not experiencing data loss and not corresponding to tracks in the first volume in the second storage system that are updated while I/O requests are being redirected to the second storage system are not subject to the second resynchronization.

8. The computer program product of claim 6 , wherein the operations further comprise:
gathering diagnostic information for repairs to the first storage system in response to the health query indicating that the first storage system is not fully operable; and
receiving a resynchronization command issued from an administrator of the first storage system in response to repairs being performed to the first storage system based on the gathered diagnostic information, wherein the received resynchronization command initiates the copying of updates to the first storage unit of the second storage system to the first storage unit of the first storage system.

9. The computer program product of claim 1 , wherein updates to a first storage unit of the second storage system mirroring the first storage unit of the first storage system are not copied to the first storage unit of the first storage system while I/O requests are being redirected to the second storage system.

10. A system for performing a failover between a first storage system and a second storage system, comprising:
at least one processor; and
a computer readable storage medium having program instructions executed by the at least one processor to perform operations, the operations comprising:
synchronizing data between the first storage system and the second storage system;
performing a failover from the first storage system to the second storage system in response to a failover event at the first storage system while synchronizing the data, wherein Input/Output (I/O) requests to the first storage system are redirected to the second storage system as part of the failover, wherein the second storage system includes a first storage unit and a second storage unit that correspond to a first storage unit and a second storage unit in the first storage system, respectively; and
in response to determining during the failover that the second storage unit is operable in the first storage system while the first storage unit in the first storage system is inoperable, initiating a resynchronization to copy updates from the second storage unit of the second storage system, mirroring the second storage unit of the first storage system, to the second storage unit of the first storage system, while I/O requests are being redirected to the second storage system.

11. The system of claim 10 , wherein the synchronization of the data between the first storage system and the second storage system are performed in synchronous copy mode and wherein the copying of the updates during the resynchronization while I/O requests are being redirected to the second storage system are performed in asynchronous copy mode.

12. The system of claim 10 ,

Assignees

• IBM

Inventors

• Brandner Michael
• Frankenberg Michael
• Mcclure Alan G
• Petersen David B
• Roman Daniel
• Spear Gail A
• Thompson John G

Classifications

• G06F11/2069 Primary

  Management of state, configuration or failover · CPC title

• G06F11/1662 Primary

  the resynchronized component or unit being a persistent storage device (re-synchronization of failed mirror storage G06F11/2082; rebuild or reconstruction of parity RAID storage G06F11/1008) · CPC title

• G06F11/2082

  Data synchronisation · CPC title

• G06F11/2071

  using a plurality of controllers · CPC title

• G06F11/2094

  Redundant storage or storage space (G06F11/2056 takes precedence) · CPC title