Modes of Operation

A ztC Edge system configured with two nodes allows you to choose from the following modes of VM availability levels of operation, depending on the system model:

Both HA operation and FT operation achieve their respective level of redundancy by using a pair of physical machines (PMs). FT operation consumes more system resources, which could possibly slow processing of applications.

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.