Config cluster with 2 nodes to start CTs and VMs with one active node only

[m1rko]

Hi all,
I am experimenting with Proxmox recently and am trying to solve an issue.
My Cluster consists of only 2 nodes,

• one main server
• one NUC (for redundancy purposes)

Additionaly there is a Synology NAS which I want to provide shared storage with.

This issue is, that the CTs and VMs on the main server, which are set to start on boot, do not start if the 2nd node is not powered up.

I found that they do startup when I set

pvecm expected 1

How can I configure the main server to execute the 'start on boot' option even though the 2nd node is not up?

Thanks a lot!

 

[bbgeek17]

A PVE cluster needs to have a majority/quorum to make any read/write decisions. In a two node cluster (which is a not supported configuration) a quorum is 2 nodes. You may know that the 2nd node is powered off, but the software doesnt - it assumes that the other node may be running and that the cluster resources might be in use already. If it didnt do so and both nodes were active at the same time, but couldnt communicate to each other, you would have data corruption.
So by executing pvecm command you inform the 1st node that it should not wait for quorum of 2, 1 is enough. If that was wrong thing to do - its on you.

You need an odd number of cluster members, with at least two being up. There are option for 3rd member, they are described here: https://pve.proxmox.com/wiki/Cluste...External Vote Support,-This section describes

---

Blockbridge : Ultra low latency all-NVME shared storage for Proxmox - https://www.blockbridge.com/proxmox

 

[m1rko]

Ok, I think I got it.
In case I set 'expected 1' and it is the only node active, I should be fine.
If Iater I do boot a 2nd node, and for example I loose network connection, bad things can happen...
So I guess I'll look into making that cluster at least 3 devices and 2 up as a minimum.
Thanks!

 

[m1rko]

Hi all, Proxmox newbies (like myself).
Just found a good Youtube channel dealing with lots of Proxmox related stuff and the 2-node home cluster issue I ran in.
Nice workaround for the "no Quorum" can be found in this video
Proxmox 2-node Homelab Cluster Quorum WITHOUT QDevice
This approach seems to work for me at this time, though I cannot say anything about data integrity issues which bbgeek brought up. So take care.
Cheers

 

[scyto]

https://forum.proxmox.com/threads/cluster-with-only-two-nodes.57766/ setup a quorum device, its easy and cheap if you can't afford to add a 3rd node at this time. (use a pi, use a vm on another machine, literally anything that has reliable network connectivity to both nodes) https://pve.proxmox.com/wiki/Cluster_Manager#_corosync_external_vote_support

 

[Dunuin]

Hi all, Proxmox newbies (like myself).
Just found a good Youtube channel dealing with lots of Proxmox related stuff and the 2-node home cluster issue I ran in.
Nice workaround for the "no Quorum" can be found in this video
Proxmox 2-node Homelab Cluster Quorum WITHOUT QDevice
This approach seems to work for me at this time, though I cannot say anything about data integrity issues which bbgeek brought up. So take care.
Cheers

Should work but keep in mind that if you shutdown the node with the 2 votes the other node with the single vote will stop working. With a third machine as a qdevice (could for example be a VM on your Synology...), no matter what node you shutdown the other node would be still operatable.

 

[m1rko]

Thanks for the advice guys.
At this time I am struggeling a bit to set up encrypted storage, then I need to shape my old Syno up to a TrueNAS Core. With these steps done I'll setup a quorum device in my NAS.