[ClusterLabs] Pacemaker startup-fencing

[Andrei Borzenkov]

On Wed, Mar 16, 2016 at 2:22 PM, Ferenc Wágner <wferi at niif.hu> wrote:
> Hi,
>
> Pacemaker explained says about this cluster option:
>
>     Advanced Use Only: Should the cluster shoot unseen nodes? Not using
>     the default is very unsafe!
>
> 1. What are those "unseen" nodes?
>

Nodes that lost communication with other nodes (think of unplugging cables)

> And a possibly related question:
>
> 2. If I've got UNCLEAN (offline) nodes, is there a way to clean them up,
>    so that they don't get fenced when I switch them on?  I mean without
>    removing the node altogether, to keep its capacity settings for
>    example.
>

You can declare node as down using "crm node clearstate". You should
not really do it unless you ascertained that node is actually
physically down.

> And some more about fencing:
>
> 3. What's the difference in cluster behavior between
>    - stonith-enabled=FALSE (9.3.2: how often will the stop operation be retried?)
>    - having no configured STONITH devices (resources won't be started, right?)
>    - failing to STONITH with some error (on every node)
>    - timing out the STONITH operation
>    - manual fencing
>

I do not think there is much difference. Without fencing pacemaker
cannot make decision to relocate resources so cluster will be stuck.

> 4. What's the modern way to do manual fencing?  (stonith_admin
>    --confirm + what?

node name.

>I ask because meatware.so comes from
>    cluster-glue and uses the old API).