[Linux-cluster] qdisk heuristic and chicken/egg dilemma

[Lon Hohberger]

On Mon, 2007-11-19 at 09:26 +0100, Reiner Rottmann wrote:
> Hi!
> 
> Say you want to configure a cluster node by using a quorum disk so that it 
> survives when the particular node runs a certain cluster service.
> 
> Such a scenario is even stated in the man page QDisk(8):
> ---%------------------------------------------------------------------------------------------------------------
> For example, a user may have a service running on one node, and that node must 
> always be the master in the event of a network partition.
> ---%------------------------------------------------------------------------------------------------------------
> 
> Then in my opinion you have a chicken/egg dilemma because you might need the 
> additional vote of the quorum disk to get a quorate cluster (which again may 
> run the rgmanager that is needed for the heuristic).

Survival after a failure is not the same thing as trying to clean-start
in a broken environment.

> How would one solve this dilemma in a straightforward way?

(a) Boot both nodes ?

(b) Manual intervention. :)

More roundabout ways include using heuristics which record state.

Admittedly we could make this a bit easier if we handle it more
gracefully inside qdiskd.

-- Lon