The image shows a Paris OCI region with three fault domains (1, 2, and 3) and a VCN that spans the three fault domains.

The VCN contains three subnets: OCI Cache cluster subnet, PostgreSQL cluster subnet, and OpenSearch cluster subnet.

In the OCI Cache cluster subnet:

• Fault domain 1: OCI Cache master node (which shows failure) tiggers the provisioning of an OCI Cache replica node.
• Fault domain 2: OCI Cache replica node is promoted to OCI Cache master node.
• Fault domain 3: OCI Cache replica node.

In the PostgreSQL cluster subnet:

• Fault domain 1: Database with PostgreSQL primary node reading and writing to database optimized storage, leveraging regional block volume (which spans across all three fault domains).
• Fault domain 2: Database with PostgreSQL replica node reading from the database optimized storage.
• Fault domain 3: Database with PostgreSQL replica node reading from the database optimized storage.

In the OpenSearch cluster subnet, all three fault domains include: OpenSearch leader node, OpenSearch Dashboard node, and OpenSearch data node.