Create VMs in antiaffinity layers for high availability

Before you begin:

Design your layers:

- You cannot rename a layer when there are deployed VMs in the layer
- You cannot move a deployed machine into a layer with a VM deployed on the same hypervisor

To create a layer:

Click the Add a layer button
Enter the layer name.
Add VMs to the layer

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Layers ensure that VMs deploy on separate hypervisors, so the following rules apply:

Layer Type	Rules
New layer	You can add any VM to a new layer
Layer with deployed VMs	You can add a VM that is not deployed You can add a powered-off VM if it deployed on a different hypervisor from the other VMs in the layer
Different layer	You cannot move a deployed VM directly to a different layer. First, power off the machine and remove the machine from the old layer, then delete the old layer. Now you will be able to add the machine to a different layer.

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Web stack use case for layers

The following diagram shows a possible anti-affinity layers use case of a simple web stack.

In Abiquo, you could deploy this configuration as follows:

ApplicationServers layer: Tomcat1, Tomcat2
DatabaseServers layer: Database1, Database2

VMs not in layers: Apache server(s), firewall, load balancer

If the deploy of a virtual appliances with layers fails, it may be because there are not enough physical machines available in your virtual datacenter. Or some physical machines may be reserved for specific enterprises, for example. Check with your system administrator.