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

Asano

Active Member
Jan 27, 2018
48
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28
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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

Proxmox Staff Member
Staff member
May 2, 2018
6,829
1,032
164
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!
 

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