If I have 2 datacenters Is it better 2 clusters or 1 ?

[drigolin]

I have to decide if create 2 clusters of 4 and 5 nodes on 2 datacenters (DC1 e DC2 linked with a dedicated 10Gb link 2ms latency) or one big cluster with 9 nodes spanning 2 datacenters.
Then a 1Gbit VLAN is present as a backup link.
Having all nodes part of a single cluster make easier migrate and replicate.
My fear is in case I loose access to an entire group of nodes, in particular case the 5 nodes remaining 4 nodes will lose quorum and all will be read only.
I don't think I will be able to restore new VM on surviving partition with a quorum lost.
Maybe I can have 5 nodes on both DC In this way I can temporary increase voting to have at least some operations possible on the remaining nodes. I don't know what is happening to my cluster when all other nodes will be back I hope corosync will be able to see what is changed... maybe I have to recreate the cluster....
We don't have shared storage on the cluster as Cephs only VMs with local storages.
If anybody would like to share real experiences or any suggestions or best practices it will be welcome.
I have proxmox backup servers on a third datacenter DC3

 

[fabian]

I would do two clusters - with backup/restore and the (still in preview) remote migration moving guests from one cluster to the other if needed shouldn't be too much of a hassle.

 

[drigolin]

I would do two clusters - with backup/restore and the (still in preview) remote migration moving guests from one cluster to the other if needed shouldn't be too much of a hassle.

Thank you Fabian, where do I found information about "remote migration"?

 

[fabian]

the "pct" and "qm" man pages (the CLI command is called "remote-migrate")