Running a single Virtual Appliance (VA) is not recommended in the vast majority of instances. Running two (or more) Virtual Appliances offers high redundancy in case of system upgrade, either within your virtual server environment or when there's a new version of the Umbrella VA available. Umbrella releases upgrades to the Virtual Appliance regularly and recommends two VAs in place in order to upgrade without interruption. To set up a second virtual appliance, simply follow the steps performed to set up the first one, or check out our documentation here.
Three key reasons to have 2 VAs are..
1. No downtime associated with upgrades
When an upgrade takes place, individual Virtual Appliances will restart and there can up to 20 minutes of downtime, depending on the size of the upgrade and whether any post-boot maintenance is required. During this time, any DNS queries routed to the Virtual Appliance will timeout and users will lose Internet connectivity. Running two Virtual Appliances ensures there is no interruption in Internet service for the users behind a Virtual Appliance.
2. The ability to schedule upgrades
Additionally, running two Virtual Appliances allows for the scheduling of update via the Dashboard. This means you can set the time to be off-hours, or during scheduled maintenance windows with ease and reliability.
3. High availability
In cases where one of the VAs were to have trouble, or you would like to potentially rebuild or move the virtual machine to another host or any other number of scenarios, having two VAs ensures you can take action with confidence your users won't be interrupted. It's always best practice to have 2 or more DNS servers and since the VA is serving that role in your network topology, the principles of high availability should be followed.