[Pacemaker] Initial quorum

[Andrew Beekhof]

On Thu, Aug 11, 2011 at 9:23 PM, pskrap <pskrap at hotmail.com> wrote:
> Andrew Beekhof <andrew at ...> writes:
>
>>
>> On Thu, Jul 21, 2011 at 4:13 PM, pskrap <pskrap at ...> wrote:
>> > Devin Reade <gdr at ...> writes:
>> >
>> >>
>> >> --On Wednesday, July 20, 2011 09:19:33 AM +0000 pskrap <pskrap at ...>
>> >> wrote:
>> >>
>> >> > I have a cluster where some of the resources cannot run on the same node.
>> >> > All  resources must be running to provide a functioning service. This
>> >> > means that a  certain amount of nodes needs to be up before it makes
>> >> > sense for the cluster to start any resources.
>> >>
>> >> Without knowing anything about your application, I would tend to question
>> >> this statement.  Is it true that you must not start *any* resources before
>> >> you have enough nodes, or is sufficient to say that the application
>> >> is not considered up until all resources are started?  It may not
>> >> make sense to run any, but does it do any harm?
>> >>
>> >> If you *can* start at least some resources before all nodes are available,
>> >> then I would expect that you could get by with defining colocation
>> >> constraints to ensure that some resources don't run on the same nodes,
>> >> perhaps augmenting things with some order constraints if necessary.
>> >>
>> >> If your applications die or do other horrible stuff when only some subset
>> >> are running then I'd have a talk with your application developers
>> >> as it sounds like a larger robustness problem.
>> >>
>> >> Devin
>> >>
>> >
>> > No, there are no crash issues etc when all resources are not running. The
>> > application is just not usable until all resources are started.
>> >
>> > As for the harm, the resources which have constraints preventing them from
>> > running will fail,
>>
>> Are you talking about constraints in the pacemaker config or some other kind?
>
> I was talking about pacemaker config constraints.

Doesn't sound very highly available though - if a failure in one node
makes the cluster useless.

>
> I found that by manually updating the expected-quorum-votes property to the
> number of nodes I want to install I can prevent pacemaker from reaching quorum
> early. It does not seem to update this property until the number of nodes
> reaches its number. Using this slight hack, pacemaker wont try to start
> anything until I have installed enough nodes.
>
> Another solution which may be better is to just to simply set the property stop-
> all-resources=true until the last machine is installed and then set it to
> false, causing everything to start.

That sounds like a better match for what you're trying to achieve.

>
>
>
>
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