[Pacemaker] again trouble with quorum (now with cman)

[Andrey Groshev]

12.07.2013, 09:15, "Digimer" <lists at alteeve.ca>:
> On 12/07/13 00:59, Andrey Groshev wrote:
>
>>  11.07.2013, 18:48, "Digimer" <lists at alteeve.ca>:
>>>  You need fencing. Specifically, cman blocks when a fence is called and
>>>  won't unblock until it's told that a fence completed successfully.
>>>  Configure cluster.conf to use 'fence_pcmk', which tells cman to pass
>>>  fence requests to pacemaker, and then configure (and test!) stonith in
>>>  pacemaker.
>>>
>>>  If you have just two nodes, be sure to also set '<cman two_node="1"
>>>  expected_votes="1" />'.
>>>
>>>  digime
>>>
>>>  On 11/07/13 09:35, Andrey Groshev wrote:
>>  I understand that it may be correct to do so...
>>  But why so difficult?
>>  Assume, I make a small НА cluster in my garage.
>>  And, I not have a managed switch or managed UPS.
>>  I can not corrupt the data.
>>  I just need to returning node as soon as possible started responding.
>
> First, fencing is not difficult, it's just one of the parts of
> clustering to learn. Second, the cluster software has no concept of
> "unimportant cluster". It treats every cluster as enterprise class.
> Third, if a service can run on both nodes without coordination with one
> another, then you don't need the cluster stack at all.
>
> Assuming you actually need to keep the service on one node or the other,
> you need to have a way to make sure the "lost" node really is lost. You
> are not allowed to make assumptions. "The only thing you know if what
> you don't know". Fencing puts a node in an unknown state (disconnected?
> frozen? crashed? blown to pieces?) and puts it into a known state,
> "off". This ensures the service can never run on both nodes at the same
> time.
>
> --
> Digimer
> Papers and Projects: https://alteeve.ca/w/
> What if the cure for cancer is trapped in the mind of a person without
> access to education?

Well, without a truly fence devices, I must use fence_pcmk?