[PVE-User] Confused about fencing device...

[Dietmar Maurer]

> Well.... That's a different approach... But still we will need an APC or whatever to make fence...
> Why this is so mandatory? With XenServer this kind of hardware is not necessary... 

Well, that is what they claim - in reality, a working fencing infrastructure is mandatory for reliable HA.

Else, you always have the risk that a VM runs on 2 nodes at the same time. Also, a single, centralized
storage is a single point of failure (SPOF), so I would not talk about HA in above scenario. 

Anyways, there are different solution - so feel free to choose what you like most ;-)

But you are probably wrong if you think all you need are 2 nodes and one cheap 
central storage. A minimum requirement is

 - redundant networking
 - redundant switch infrastructure
 - redundant power supplies
 - redundant storage
 - UPS for all devices

So the need for the additional fencing infrastructure is quite negligible here (cheap add-on to UPS devices).

HA is nothing you get for free ;-)