quorum even node number

Hi,

even node numbers are no problem.
if you have 4 nodes you can have 1 node offline without any problems.

Changing the votes is no good idea because you give one node more weight then other ones.
 
So, any number of nodes greater than 3 is totally safe? What would happens in a 4 nodes cluster if 2 nodes are down ? You loose the quorum. The same for 6 nodes: 3 up, 3 down.
 
You will always need majority among nodes. The formula for number of running nodes to achieve quorum is: floor((n/2)+1) for n > 0.
 
Yes but with an even number of node there is the very remote possibility that half cluster goes down (power failures or so on)
With an odd number this is not possible.

This could be solved by placing a single node with less redundancy level then the majority of nodes. In example: one PSU and no redundant network.
 
I don't get your point. Why is the chance for loosing more than one node at the same time higher with a cluster of even nodes compared to a cluster with uneven nodes?
 
It depends on the server model. If you have one PSU and 20 nodes, 10 connected to feed1, 10 connected to feed2, if you loose feed1, you loose half cluster, thus, no quorum.
 
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