Modes of Operation

An everRun system provides the following modes of operation to set user-defined availability levels for VMs:

Both HA operation and FT operation achieve their respective level of redundancy by using a pair of physical machines (PMs).

Stratus recommends configuring quorum service for both HA operation and FT operation. The quorum service prevents a condition called split-brain where both PMs of an HA operation and FT operation pair are running independently of each other; for information, see Quorum Servers.

In unprotected operation, a VM runs on only one PM; if that PM shuts down or fails, the VM will not fail over to the second PM. Use unprotected operation only if a VM has specific requirements to do so, for example, if software licensing restrictions prevent your applications from being installed or running at the same time on both PMs for redundancy.