[ClusterLabs] DLM fencing

[Ferenc Wágner]

Ken Gaillot <kgaillot at redhat.com> writes:

> On 02/07/2016 12:21 AM, G Spot wrote:
> 
>> Thanks for your response, am using ocf:pacemaker:controld resource
>> agent and stonith-enabled=false do I need to configure stonith device
>> to make this work?
>
> Correct. DLM requires access to fencing.

I've ment to explore this connection for long, but never found much
useful material on the subject.  How does DLM fencing fit into the
modern Pacemaker architecture?  Fencing is a confusing topic in itself
already (fence_legacy, fence_pcmk, stonith, stonithd, stonith_admin),
then dlm_controld can use dlm_stonith to proxy fencing requests to
Pacemaker, and it becomes hopeless... :)

I'd be grateful for a pointer to a good overview document, or a quick
sketch if you can spare the time.  To invoke some concrete questions:
When does DLM fence a node?  Is it necessary only when there's no
resource manager running on the cluster?  Does it matter whether
dlm_controld is run as a standalone daemon or as a controld resource?
Wouldn't Pacemaker fence a failing node itself all the same?  Or is
dlm_stonith for the case when only the stonithd component of Pacemaker
is active somehow?
-- 
Thanks,
Feri.