One question for Proxmox VE cluster

[chris2022]

Hi,
We have a cluster of two nodes and one of nodes needs to be moved to another physical location. The node that will be moved needs to be powered off at current location and powered on at the new location. The other cluster node needs keep running during movement. Does anyone know how to do before moving node? After the movement of node, just powering on node can get it back in the cluster?

Kind regards,
Chris

 

[mira]

If you don't change anything regarding the cluster config, the second node should connect without any issues after the move.

As you lose quorum during that time (<= 50% of votes), you can't start or stop VMs, or run any other actions that require quorum during that time.
If you still need to do something that requires quorum, you can set the expected votes (pvecm expected 1) on that node. But do this only if you absolutely know the other node is offline, as otherwise this can lead to issues and corruption.

 

[Tmanok]

The simplest solution to avoid breaking things before the move would be to add witness nodes (any machine but not VM) to balance your cluster's quorum. If you are not really running a production deployment (which should have a minimum of 3 nodes) then you can use a run of the mill machine with a good enough NIC and a quad core CPU with 8GB of RAM. Later you can decommission these quorum nodes.

In the future it would be nice if there was a more stable and supported method of adding and removing nodes from a cluster, but for now this will work and is very simple to setup.

 

[chris2022]

If you don't change anything regarding the cluster config, the second node should connect without any issues after the move.

As you lose quorum during that time (<= 50% of votes), you can't start or stop VMs, or run any other actions that require quorum during that time.
If you still need to do something that requires quorum, you can set the expected votes (pvecm expected 1) on that node. But do this only if you absolutely know the other node is offline, as otherwise this can lead to issues and corruption.

Thanks Mira. If the IP needs to be changed after the node is moved, will it break the cluster ? and how to do at this case?

 

[chris2022]

The simplest solution to avoid breaking things before the move would be to add witness nodes (any machine but not VM) to balance your cluster's quorum. If you are not really running a production deployment (which should have a minimum of 3 nodes) then you can use a run of the mill machine with a good enough NIC and a quad core CPU with 8GB of RAM. Later you can decommission these quorum nodes.

In the future it would be nice if there was a more stable and supported method of adding and removing nodes from a cluster, but for now this will work and is very simple to setup.

Thanks Tmanok. Currently, we do not have a free and powerful machine to be set up as witness node.

 

[chris2022]

Thanks Mira. If the IP needs to be changed after the node is moved, will it break the cluster ? and how to do at this case?

Mira, if we set (pvecm expected 1) after the moving node is power off, what do we need to do after the moved node is powered up at the new location? thanks.

 

[mira]

Thanks Mira. If the IP needs to be changed after the node is moved, will it break the cluster ? and how to do at this case?

Do you know that before shutting down the node to move it?
If so, you could already change the Corosync config to adapt it, right before shutting it down.

Otherwise it involves a few more steps.


The expected votes will be reset once the 2nd node joins.

 

[chris2022]

If you don't change anything regarding the cluster config, the second node should connect without any issues after the move.

As you lose quorum during that time (<= 50% of votes), you can't start or stop VMs, or run any other actions that require quorum during that time.
If you still need to do something that requires quorum, you can set the expected votes (pvecm expected 1) on that node. But do this only if you absolutely know the other node is offline, as otherwise this can lead to issues and corruption.

mira, If I can set the expected votes(pvecm expected 1) , what will I need to do after the other node is back online or before the node is up? thanks.

 

[chris2022]

mira, If I can set the expected votes(pvecm expected 1) , what will I need to do after the other node is back online or before the node is up? thanks.

mira, sorry. I missed your reply on this question. You said "The expected votes will be reset once the 2nd node joins.". Does it mean that the expected votes will be reset automatically once the 2nd node joins? Thanks.

 

[mira]

Yes, as soon as it joins, the expected votes will be `2` again.

 

[chris2022]

Yes, as soon as it joins, the expected votes will be `2` again.

Thanks mira.