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

[Asano]

Hi,

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 https://pve.proxmox.com/wiki/Multicast_notes 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?

Thanks!

 

[Stoiko Ivanov]

Hi,

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: https://pve.proxmox.com/pve-docs/pve-admin-guide.html#_corosync_configuration

hope this helps!

 

[Asano]

Thanks for the info and link, I will not switch then as everything runs really smooth