[Linux-cluster] Dependency graphs, order of startup and failover handling

[Eftychios Eftychiou]

Thanks for clarifying those issues for me. I was hopping that dependency
graphs would be possible with the current version. Are the dependency
changes, that you are working on currently, to be included in the RHEL4?

Unfortunately since the planned cluster will run mission critical systems
everything installed should be officially supported by RedHat hence if it is
not part of RHEL4 then I cannot recommend it. On the other hand I would love
to try it out ;) The dependencies involved in our system are rather complex
and would be a nice proving ground.

What worries me though is this

"Fencing in a two node cluster according to the FAQ could lead to each node
trying to fence each other resulting in total cluster blowup. The suggested
solution of that problem was to use serialized fencing devices. From my
understanding the above scenario can occur because in a two node environment
each node has 1 vote so there is no way to break the tie. In any case in a
total unrelated section it is mentioned that a quorum disk can be used to
break the tie. Well I am a bit confused since in the section it was
mentioned that quorum disk support was initially removed from RHEL4 but then
was added optionally. What is the proper way to create a two node cluster ?
Is quorum disk required if a serialized fence device is used? Will quorum
disks usage be phased out in the future ? If yes how do you plan to address
the issues in a 2 node cluster?"

Thanks again,
Efty




On 12/8/06, Lon Hohberger <lhh at redhat.com> wrote:
>
> On Fri, 2006-12-08 at 13:08 -0500, Lon Hohberger wrote:
>
> > Application of those operations and running it through graphviz (dot)
> > yields the attached png as a result.
> >
> > (come on, you gotta run it through graphviz!)
>
> Note: I hope to fix the big remaining bug in the algorithm soon; maybe
> early next week, and commit the test program to CVS.  Integration will
> take some time, and I'm need to document "how this works" reasonably
> well.
>
> -- Lon
>
>
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>
>
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