This image contains an Oracle Cloud Infrastructure region containing a single availability domain which itself contains three fault domains, Fault Domain 1, Fault Domain 2, and Fault Domain 3. A virtual cloud network (VCN) within the resgion spans the availability domain and all three fault domains. The VCN contains both a public subnet and a private subnet, which both span the three fault domains. Both subnets are protected by a routing table and a security list. Monitoring, Auditing, and Identity services are provided within the region but external to the VCN.

• The public subnet contains a load balancer tier in which fault domain 1 contains an active load balancer and fault domain 2 contains a passive load balancer. Traffic to this tier from the VCN is controlled by a security list and a routing table.
• Below the load balancer tier subnet is a private subnet containing the web server tier, comprising two Drupal web servers, one in each of fault domains 1 and 2.
• Below that, a private subnet contains a file storage tier, with network file storage (NFS) in fault domain 2. Access to this tier is controlled by a network security group (NSG).
• The bottom private subnet contains three MySQL database systems, one in each of the three fault domains. The DB system in fault domain 1 is the primary while the other two are secondary. Traffic to this tier from the VCN is controlled by a security list and a routing table.

Users external to the region access the Load Balancer tier via an Internet Gateway. The load balancer then directs traffic to the available Drupal webserver in either fault domain 1 or 2. These servers also pull data from the MsSQL database systems in the private subnet.