Is it worth switching from an unicast to a multicast cluster?


Well-Known Member
Jan 27, 2018

one of my projects uses a Proxmox unicast cluster at Hetzner. A few month ago Hetzner introduced vSwitches and from my first impression they work very well. Meanwhile all cluster nodes have a bridged interface on a shared vSwitch which is also already used for all VMs. On this interfaces mulitcasting works as well and therefore I could use them for the cluster nodes itself as well.

But is switching to multicast worth it in this case? The cluster for this project will never exceed 4 nodes and was/is running stable since setup (besides zfs replication failures once in a while but I doubt they are an unicast problem, also idk). Are there more benefits from multicast (besides unicast being the last resort and the node limit has not much further info)?

Assuming it would be worth it, could I "simply" change /etc/pve/corosync.conf and do a cluster restart on each node or are there more places I'd need to attend to and maybe other pitfalls I should be aware of?


In general if your cluster runs stable with unicast and the node-count is/remains low - I'd say - don't touch a running system.
The downside of unicast is, that you need to transmit more network-packets to the switch vs. multicast, but if your network can handle that and keeps it latency low - no need to touch it.

As for the changing of the corosync.conf - That's nicely explained in our reference-documentation:

hope this helps!


The Proxmox community has been around for many years and offers help and support for Proxmox VE, Proxmox Backup Server, and Proxmox Mail Gateway.
We think our community is one of the best thanks to people like you!

Get your subscription!

The Proxmox team works very hard to make sure you are running the best software and getting stable updates and security enhancements, as well as quick enterprise support. Tens of thousands of happy customers have a Proxmox subscription. Get yours easily in our online shop.

Buy now!