What is a shadow instance?

A shadow instance is a temporary instance created during a switchover or a disaster recovery drill. It is used to write data in real time to the recovery site. This instance exists only during the data replication phase and is automatically deleted after you confirm that the failover is complete.

• The instance is created from an HDR Alibaba Cloud Image. Its operating system and instance type may differ from the source instance. To reduce costs, HDR prioritizes using shared-resource instances as shadow instances.
• To ensure a smooth disaster recovery, do not modify the shadow instance. For example, do not change the instance password, start or stop the instance, attach or detach cloud disks, attach or detach elastic network interfaces (ENIs), or add or remove security groups.

During a switchover or disaster recovery drill, a new instance is created to run your services.