Why 3 nodes for HA cluster?

[welbers]

Hello,

I'm sorry for the question. But why do I need at least 3 nodes for a HA cluster? This is stated in:

http://pve.proxmox.com/wiki/High_Availability_Cluster#System_requirements

In my opinion 2 nodes should be enough for active failover situations or am I wrong? I'm newby concerning clustering.

I love Promox and want to build a HA cluster with 2 nodes and a ZFS-based Nextena-Storage solution which acts as shared storage for all clients and data. The shared storage has a dual-10Gbit-nic and I want to put a 10Gbit-nic in every of the 2 nodes to have the best possible and fastes access. The storage should be accessible via iSCSI.

Is this solution possible or doesn't it work with Proxmox as HA cluster?

Thx in advance,
Andreas

 

[GT1]

But why do I need at least 3 nodes for a HA cluster?

to avoid a split brain condition.

 

[welbers]

Ok, I understand the idea.

But it should also be possible to avoid split-brain using redundant heartbeat-connections or not?

3 hosts is very expensive if I only need 2 hosts. Is it also possible to build HA-clustering in Proxmox if I use redundant heartbeat?

 

[udo]

Ok, I understand the idea.

But it should also be possible to avoid split-brain using redundant heartbeat-connections or not?

3 hosts is very expensive if I only need 2 hosts. Is it also possible to build HA-clustering in Proxmox if I use redundant heartbeat?

Hi,
no you need an quorum disk - the server which see the quorum-disk has enough quorum for working if one server died (or has network trouble).

Udo

 

[Michel Samovojski]

why not make a possible virtual node? some starter san have it.

 

[dietmar]

why not make a possible virtual node?

That makes no sense to me (you can assign arbitrary number of votes if you want that).