In HA mode, you specify that this VM must be running. If its not do a list of certain actions. But the thing is, making your app crash gracefully can be incred

In HA mode, you specify that this VM must be running. If its not do a list of certain actions. But the thing is, making your app crash gracefully can be incredibly hard, and can almost always take a lot of dev time. its cheaper in terms of planning and execution to have two have an HA pair defined in the cluster, and another HA pair defined in software (i.e. behind a varnish node or the like) You can have virtual IPs so that if a node is not responding the HA partner picks up the traffic. If thats properly locked up, the hypervisor can kill the machine and restart it. as for: >migrate from overloaded hosts: just crash container. try doing that with a clustered something, the host becomes overloaded, kills the app. not only does the traffic shift off to other nodes(which might already be started to overload), it takes resources to sync back into the cluster. You don't want this behaviour as it causes failure hysteresis. (that is, as soon as you start to reach breaking point, the whole thing collapses and refuses to come back up, without stopping incoming traffic)