question about a master node crash in a pool.

oliv77

Hi,

We are currently using an XCP-ng pool with an XOA (Xen Orchestra) instance hosted within the same pool.

Recently, we encountered a crash of the Master node. At that precise moment, we had disabled High Availability (HA) for specific maintenance on the pool that had been performed a few days prior .
Although the XOA VM remained operational on a Slave node, we found ourselves in a "blind management" situation: the XOA interface could no longer communicate with the pool because the XAPI entry point (the Master) was down.

To avoid this scenario in the future, I would appreciate your opinion on the feasibility and best practices regarding the following points:
Out-of-band management: Is it recommended to move XOA to a physical server (or a management pool) completely independent of the production pool it manages to ensure visibility in case of quorum loss?

Cross-Configuration: If we have two separate pools (Pool A and Pool B), is it advisable to host XOA-A on Pool B to manage Pool A, and vice versa?
High Availability (HA) Behavior: Even with HA enabled, while the system elects a new Master and the XAPI stack restarts, will there always be a period of unavailability for the XOA interface?
We are looking to ensure that our management tools remain available and "visible" even in the event of a critical Master failure.

Thank you in advance for your advice and for all the work done on XCP-ng.

Best regards
Olivier

olivierlambert

Hi,

In that case, the easiest thing to do is:

wait for the master to get back
or if it won't come back, to elect a slave as the new master (one CLI command to run and you are done)

It's very straightforward. It shouldn't be a dreaded scenario, because as soon as you lose management, you know it and it doesn't impact the rest of your VMs. Even without HA, it's a pretty easy situation to solve.

Note it shouldn't happen that often, as long as you have a documented procedure, it should be enough to deal with it.

oliv77

Ok, thank you very much for this informations

So, regarding cross-configuration: If we have two separate pools (Pool A and Pool B), is it advisable to host XOA-A on Pool B to manage Pool A, and vice versa?

Is this an impractical option (or is there another one?)

Pilow

@oliv77 you should let your XOA in the right pool I guess

as the networks are defined at pool level, that would need you to be sure networks in pool A (and management IPs of HOSTs in pool A) are available to XOA-A placed in pool B

can be done, but why the head ache ?
master down have no impact on VM running on other hosts in the pool
master of PoolA down, no bonus having XOA-A in pool B, you are still blind as long as Pool A doesn't recover its master.

olivierlambert

You can have one XO on another pool, this won't change the if the master is down, you have to restart it or elect a new one anyway. You can also have 2x XOAs managing the same pool, it's OK (just don't mix backup jobs)

oliv77

Hi @olivierlambert and @pilow

Thank you for your answers, it helps a lot,

Regards,

Olivier