RDS Multi-AZ Failover Cause

Question

Our database had a multi-az failover on April 14th, and the Event Logs said "The primary host of the RDS Multi-AZ instance is unreachable due to loss of network connectivity." I would like to confirm that the cause was a hardware failure and not a data issue or something like that.

Answer

Hello.

I thought the following documentation would show that this can occur outside of hardware failure.  
For example, I thought that if I changed the network ACL settings of the RDS subnet and made it impossible to communicate with other subnets, I could create a state where it could not communicate with the primary instance, so I could fail over under the same conditions.  
Also, if there is a hardware failure, a notification will be sent on the service health dashboard, etc.  
Even if the notification was not sent, I think it would be possible to contact AWS Support to find out if a hardware failure occurred at that time.  
https://repost.aws/knowledge-center/rds-multi-az-failover-restart  
> The primary host of the RDS Multi-AZ instance is unreachable due to loss of network connectivity: This reason indicates that the Multi-AZ failover and database instance restart were caused by a transient network issue that affected the primary host of your Multi-AZ deployment. The internal monitoring system detected this issue and initiated a failover.

RDS Multi-AZ Failover Cause

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