Key component 3 – a fencing device
So, we have talked about the two key components of a Proxmox HA cluster; they are the storage devices and reliable network. Do you remember that I mentioned a fencing device when I introduced DRBD? Do you know what a fencing device is and how it works? We'll learn more about this in the following section.
What is a fencing device?
A fencing device, as the name suggests, is a virtual fence that prevents communication between two nodes. It is used to separate the failed node from accessing shared resources. If there are two nodes that access shared resources at the same time, a collision occurs; this might corrupt the shared data, which is the data inside the VM.
Such fencing is done automatically based on the configuration defined, because we cannot identify a real failure or a temporary hang on a node. If a node is really down, then a fencing action is not needed, but if it is a temporary hang due to a network delay or temporary resource shortage...
