Hey Guys,
I’m testing out my first HA cluster in xcp-ng consisting of 3X servers and shared storage via TrueNas.
I used the command:
xe pool-ha-enable heartbeat-sr-uuids={storage id}
to enable HA and add the heartbeat to my shared SR.
So far it’s working as expected.
Now I’d like to enable HA on a second shared SR, but can’t find any documentation on how to do this.
I tied to do
xe pool-ha-enable heartbeat-sr-uuids={ID of 2nd SR}
but I get the error:
The operation could not be performed because HA is enabled on the Pool
I have never tried enabling two heartbeats and I am not sure if that is possible.
Maybe I’m confused about the process. I assumed that all HA enabled VMs needed to exist on the HA SR.
After a little more reading, it appears that the HA SR is used to store Metadata and Statefile for the HA cluster. Basically a shared meeting point for all of the servers to exchange information. The physical location of the VMs can be on other shared SR.
Am I understanding that correctly?
The metadata is maintained by the master host and replicated in all the other hosts. The importance of using an SR as a heartbeat is to solve the “Split Brain” problem which as far as I know in Xen can have only one.
Also, HA is not needed to have a VM start on any host from a shared storage nor is it needed to live migrate a VM between hosts. HA is only needed if you want a scenario where a host goes dark and you wan the VM’s marked as HA to start automatically without any interaction on one of the remaining hosts.
Thanks for the reply!
That’s exactly what I want it for.