A partial failover is the scenario where you still have infrastructure up and running, and only one or more virtual machines are having issues. In this situation, a complete site failover isn’t required to solve the issue. Partial failover allows you to start the replica VM of one or more VMs at Zettagrid and let all the other VMs continue to run at your client side. To make this possible, the technology integrated into the Network Extension Appliance extends any customer network to Zettagrid, so that production VMs can communicate with replicas without any change in the IP addressing. This happens by the NEA creating a Layer 2 VPN tunnel for each network involved that transparently extents the tenant network to the corresponding Zettagrid provided network.
Virtual machines running at Zettagrid reach the internet by using the internet connection at the client side. Any packet created at Zettagrid, and with a destination other than its own subnet, is forwarded to the default gateway, which is running at the client side.
During a partial failover, only single replica VMs are selected to be powered on at Zettagrid. Those VMs will be able to connect to their original network at the client side..This is achieved by the Network Extension Appliance. In a Partial failover scenario, there are two NEAs involved in the process:
- The NEA deployed at the client has one network interface connected to the same port group as the virtual machines (multiple appliances are deployed when the end user has multiple port groups with VMs). The NEA starts the OpenVPN client and connects to the Zettagrid cloud Connect Gateways and through to the NEA deployed at Zettagrid.
- The network appliance at the service provider side receives the connections from the OpenVPN client thanks to an OpenVPN server running inside it. The result is the creation of a L2 tunnel between the two sites. On top of the L2 tunnel, a Proxy ARP solution running inside both network appliances forwards L2 packets from one side to the other, and vice versa. The result is that VMs can use the same subnet or broadcast domain, regardless of the site where they are powered on.
- On top of the L2 tunnel, a Proxy ARP solution running inside both network appliances forwards L2 packets from one side to the other, and vice versa. The result is that VMs can use the same subnet or broadcast domain, regardless of the site where they are powered on.
Network Extension Appliance Deployment at Client Side:
Depending on different scenarios that may apply at the client end, the Network Extension Appliance will be deployed at the tenant side
- At setup time new customers the NEA is deployed during the service provider setup wizard;
- For existing customer already consuming backup resources, the NEA deployment is requested by Veeam Backup & Replication during the first partial failover attempt.
The wizard tries to automatically choose the best network to connect the NEA, but it’s extremely important that you edit the configuration of the NEA so that it is connected to the same network of the VMs being replicated at Zettagrid The client side NEA has only one network interface. If you have ordered multiple networks, one NEA will be deployed for each network.
Limitations of Partial Failovers
- Veeam Backup & Replication supports one failover operation type at a time. If a cloud failover plan during partial site failover, Veeam Backup & Replication will suggest that the VM involved in the partial site failover process is processed with the cloud failover plan.
- A partial site failover can only be done for those VMs that have a static IP address.