When a node fails, a virtual hot standby node instance starts automatically, detaches the EBS storage of the failed node, configures a new instance, reattaches the EBS storage to the new instance, and the configuration is reinstated.
If a node fails and another instance cannot be provisioned in the same placement group, or if you have issues with EBS data in the EBS volume, the system continues to run on Fallback. Contact Teradata Customer Support to spin up a new instance in the placement group and start Fallback recovery.