[PVE-User] Newbie in cluster - architecture questions

[Thomas Lamprecht]

Hi,

On 2/17/20 2:21 PM, Demetri A. Mkobaranov wrote:
> 1) From the Proxmox manual it seems like a cluster, without HA, offers just the ability to migrate a guest from a node to another one. Is this correct?

That plus some other things:
* you can manage all nodes through connecting to any node (multi master system)
* replicate ZFS backed VMs easily between nodes
* define backup jobs for VMs or resource pools and they'll run independently where the VM currently is.

> 
> 1B) Basically the configuration of one node is replicated (like /etc/pve via pmxcfs) on other nodes so that they are all aware of the guests and then corosync makes each node aware of the status of any other node and probably triggers the synchronization via pmxcfs. Right? Nothing more (unless further configuration) ?

Yeah, basically yes. A Proxmox VE base design is that each VM/CT belongs
to a node, so other nodes must not touch them, but only redirect API calls
and what not to the owning node.

And yes, all VM/CT, storage, firewall and some other configuration is on
/etc/pve and that is a realtime shared configuration file system. Any change
to any file will get replicated to all nodes in a reliable, virtual synchronous,
way.

> 
> 2) Can I have nodes belonging to one cluster but living in different countries? Or in this case a multi-cluster is required (like 3 nodes in one datacenter and a cluster in another datacenter somehow linked together) ?
> 

Theoretically yes, practically not so.
Clustering has some assertions on timing, so you need LAN like latencies between
those nodes. It can work with <= 10 milliseconds but ideal are <= 2 milliseconds
round trip times.

Linking clusters is planned and some work is going on (the API Token series was
preparatory work for linking clusters) but it is not yet possible.

hope that clears things up a bit.

cheers,
Thomas