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22.4. Upgrading an HA Cluster

The software versions running on the master and slave units in an HA cluster should be the same. When a new software version becomes available and is to be installed on both units, the upgrade is performed on one unit at a time.

The central principle in the cluster upgrade process is that upgrading the inactive unit will not affect the operation of the cluster and only momentarily make the inactive unit unavailable.

HA Upgrade Steps

The sequence of steps for an HA version upgrade is the following:

  1. Identify which unit is inactive and upgrade it first, as though it was standalone.

  2. When the inactive unit is once again synchronized with the active unit, manually cause a handover to occur so that the inactive becomes the active unit.

  3. Now upgrade the inactive unit as though it was standalone. Both units will then resynchronize and both will have the new software version.

The above steps will now be broken down into more detailed descriptions.

A. Identify which is the inactive unit in the cluster

The currently inactive unit will be upgraded first so it is necessary to identify it. To do this, connect a CLI console to one of the cluster units and issue the ha command. Some typical output if the unit is active is shown below. 

System:/> ha
		
This device is a HA SLAVE
This device is currently Active (for 51m 29s)
HA cluster peer is ALIVE
HA object sync: 100%

This unit is the currently active unit, so the other one is the inactive unit.

B. Upgrade the inactive unit

Once the inactive device is identified, upgrade it with the new software version. This is done exactly as though the device were a standalone device and not in a cluster. The upgrade procedure is described in Section 2.5, Upgrading Software.

[Important] Important: Ensure the inactive unit is fully synchronized

Before going to the next step make sure the inactive unit is fully operational and also fully synchronized with the active unit after the software upgrade completes.

To confirm this, issue the CLI ha command on the inactive unit. The output from the command should indicate that the object synchronization is 100%, as shown in the example output below: 

System:/> ha
			
This device is a HA SLAVE
This device is currently Inactive (for 45s)
HA cluster peer is ALIVE
HA object sync: 100%

C. Manually cause a handover to occur

Now, connect to the active unit (which is still running the old software version) with a CLI console and issue the ha -deactivate command. This will cause a handover to occur so the active unit becomes inactive, and the inactive unit becomes active. 

System:/> ha -deactivate
			
Performing deactivation.

To check that the handover has completed successfully, the ha command can be entered again and the text "Inactive" and "is ALIVE" should appear in the output.

D. Upgrade the newly inactive unit

When the handover is complete, upgrade the newly inactive unit with the new software version. Just as in step B, this is done in the normal way, as though the unit were standalone and not part of a cluster.

E. Wait for resynchronization

Once the second software upgrade is complete, two HA peers will automatically resynchronize and the cluster will continue operation. The roles of active and inactive unit will now have been reversed.

If it is desirable to make the active unit inactive, and the inactive unit active, the CLI command ha -activate can be entered on the inactive unit.

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