# US 11,307,944 B2 · Automated failover for asynchronous remote copy

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- Number: US 11,307,944 B2
- Document ID: US11307944B2
- Status: Granted
- Kind: B2
- Application number: 16/892,636
- Filed: 2020-06-04
- Published: 2021-12-09
- Granted: 2022-04-19
- Earliest claimed: 2020-06-04
- Assignees: Hitachi, Ltd.
- Applicants: Hitachi, Ltd.
- Inventors: Tomohiro Kawaguchi
- Web page: https://patentgrep.com/patent/US11307944B2

## CPC

- G06F 11/2023: {Failover techniques}
- G06F 11/2094: {Redundant storage or storage space (G06F11/2056 takes precedence)}
- G06F 11/0772: {Means for error signaling, e.g. using interrupts, exception flags, dedicated error registers}
- G06F 11/1461: {Backup scheduling policy}
- G06F 11/1464: {for networked environments}
- G06F 11/1466: {to make the backup process non-disruptive}
- G06F 11/1469: {Backup restoration techniques}
- G06F 11/2097: {maintaining the standby controller/processing unit updated (initialisation or re-synchronisation thereof G06F11/1658 and subgroups)}
- G06F 16/1734: {Details of monitoring file system events, e.g. by the use of hooks, filter drivers, logs}
- G06F 16/1815: {Journaling file systems}
- G06F 2201/81: Threshold
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)

## Abstract

Example implementations described herein are directed to automated failover and assuring RTO (Recovery Time Objective) assurance, and RPO (Recovery Point Objective) on asynchronous remote copy feature of storage. By using markers that are cyclically stored to the journal volume, the storage device can thereby determine an accurate communication loss period.

## Claims

### Claim 1

A method for managing an asynchronous copy pair between a first storage system managing a primary volume and a second storage system managing a secondary volume, the primary volume and the secondary volume configured to be the asynchronous copy pair configured to manage copy operations through a primary journal and a secondary journal, the method comprising:
storing, at the first storage system, a marker indicative of a current time to the primary journal;
determining, at the first storage system, if no access has occurred from the second storage system to the primary journal for a first threshold period of time;
for the determining at the first storage system indicative of no access from the second storage system for more than the first threshold period of time, suspending time operations between the primary volume and the secondary volume;
determining, at the second storage system, if no marker is provided to the secondary journal for a second threshold period of time;
for the determining at the second storage system indicative of no marker being provided for more than the second threshold period of time, suspending copy operations for the asynchronous copy pair.

### Claim 2 (depends on 1)

The method of claim 1, further comprising managing a state for the asynchronous copy pair, comprising:
for a storage device of the primary volume becoming unreachable, changing the state of the asynchronous copy pair to a first state of accepting I/O to the primary volume and duplication being unavailable;
during the first state, for the storage device of the primary volume failing to obtain a leader from a quorum device, changing the state of the asynchronous copy pair to no longer accept I/O to the primary volume;
for another storage device of the secondary volume becoming unreachable, changing the state of the asynchronous copy pair to a second state of not accepting I/O to the secondary volume and duplication being unavailable; and
during the second state, for the another storage device of the secondary volume becoming the leader from the quorum device, changing the state of the asynchronous copy pair to accept I/O to the secondary volume.

### Claim 3 (depends on 1)

The method of claim 1, wherein the method is executed at time cycles determined based on a recovery time objective or a recovery point objective.

### Claim 4 (depends on 1)

The method of claim 1, wherein the first storage system and the second storage system is communicatively coupled to a quorum volume managing leader information for the primary volume, and a previous access time to the quorum volume by each of the primary volume and the secondary volume;
wherein the determining, at the first storage system, if no access has occurred from the second storage system to the primary journal for the first threshold period of time is based on the previous access time to the quorum volume by the secondary volume.

### Claim 5 (depends on 1)

The method of claim 1, further comprising, for an occurrence of a path failure to an application:
for a state of the asynchronously copy pair indicative of the asynchronous copy pair not accepting Input/Output (I/O), stopping the application;
for a state of the asynchronous copy pair indicative of the secondary volume being a leader and is accepting the I/O, conducting a failover to the secondary volume.

### Claim 6 (depends on 1)

The method of claim 1, further comprising, for receipt of an inquiry for configuration information:
for a state of the asynchronous copy pair indicative of the asynchronous copy pair being already established, responding to the inquiry with a volume ID of the primary volume; and
for a state of the asynchronous copy pair indicative of the asynchronous copy pair undergoing a process to be established, responding to the inquiry with the volume ID of one of the primary volume and the secondary volume indicated as a leader.

### Claim 7 (depends on 1)

The method of claim 1, further comprising suspending Input/Output (I/O) from a host to the primary volume during the storing of the marker.

### Claim 8

A non-transitory computer readable medium, storing instructions for managing an asynchronous copy pair between a first storage system managing a primary volume and a second storage system managing a secondary volume, the primary volume and the secondary volume configured to be the asynchronous copy pair configured to manage copy operations through a primary journal and a secondary journal, the instructions comprising:
storing, at the first storage system, a marker indicative of a current time to the primary journal;
determining, at the first storage system, if no access has occurred from the second storage system to the primary journal for a first threshold period of time;
for the determining at the first storage system indicative of no access from the second storage system for more than the first threshold period of time, suspending time operations between the primary volume and the secondary volume;
determining, at the second storage system, if no marker is provided to the secondary journal for a second threshold period of time;
for the determining at the second storage system indicative of no marker being provided for more than the second threshold period of time, suspending copy operations for the asynchronous copy pair.

### Claim 9 (depends on 8)

The non-transitory computer readable medium of claim 8, the instructions further comprising managing a state for the asynchronous copy pair, comprising:
for a storage device of the primary volume becoming unreachable, changing the state of the asynchronous copy pair to a first state of accepting I/O to the primary volume and duplication being unavailable;
during the first state, for the storage device of the primary volume failing to obtain a leader from a quorum device, changing the state of the asynchronous copy pair to no longer accept I/O to the primary volume;
for another storage device of the secondary volume becoming unreachable, changing the state of the asynchronous copy pair to a second state of not accepting I/O to the secondary volume and duplication being unavailable; and
during the second state, for the another storage device of the secondary volume becoming the leader from the quorum device, changing the state of the asynchronous copy pair to accept I/O to the secondary volume.

### Claim 10 (depends on 8)

The non-transitory computer readable medium of claim 8, wherein the instructions are executed at time cycles determined based on a recovery time objective or a recovery point objective.

### Claim 11 (depends on 8)

The non-transitory computer readable medium of claim 8, wherein the first storage system and the second storage system is communicatively coupled to a quorum volume managing leader information for the primary volume, and a previous access time to the quorum volume by each of the primary volume and the secondary volume;
wherein the determining, at the first storage system, if no access has occurred from the second storage system to the primary journal for the first threshold period of time is based on the previous access time to the quorum volume by the secondary volume.

### Claim 12 (depends on 8)

The non-transitory computer readable medium of claim 8, further comprising, for an occurrence of a path failure to an application:
for a state of the asynchronously copy pair indicative of the asynchronous copy pair not accepting Input/Output (I/O), stopping the application;
for a state of the as the asynchronous copy pair indicative of the secondary volume being a leader and is accepting the I/O, conducting a failover to the secondary volume.

### Claim 13 (depends on 8)

The non-transitory computer readable medium of claim 8, further comprising, for receipt of an inquiry for configuration information:
for a state of the asynchronous copy pair indicative of the asynchronous copy pair being already established, responding to the inquiry with a volume ID of the primary volume; and
for a state of the asynchronous copy pair indicative of the asynchronous copy pair undergoing a process to be established, responding to the inquiry with the volume ID of one of the primary volume and the secondary volume indicated as a leader.

### Claim 14 (depends on 8)

The non-transitory computer readable medium of claim 8, further comprising suspending Input/Output (I/O) from a host to the primary volume during the storing of the marker.