On Tue, 2010-10-05 at 09:07 -0500, Kevin Grittner wrote:
> Simon Riggs <simon@2ndQuadrant.com> wrote:
> > Robert Haas wrote:
> >> Simon Riggs <simon@2ndquadrant.com> wrote:
> >>> Josh Berkus wrote:
> >>>>>>> Quorum commit, even with configurable vote weights, can't
> >>>>>>> handle a requirement that a particular commit be replicated
> >>>>>>> to (A || B) && (C || D).
> >>>>>> Good point.
> >>>
> >>> Asking for quorum_commit = 3 would cover that requirement.
> >>>
> >>> Not exactly as requested,
>
> >> That's just not the same thing.
> >
> > In what important ways does it differ?
>
> When you have one server functioning at each site you'll block until
> you get a third machine back, rather than replicating to both sites
> and remaining functional.
And that is so important a consideration that you would like to move
from one parameter in one file to a whole set of parameters, set
differently in 5 separate files? Is it a common use case that people
have more than 3 separate servers for one application, which is where
the difference shows itself.
Another check: does specifying replication by server in such detail mean
we can't specify robustness at the transaction level? If we gave up that
feature, it would be a great loss for performance tuning.
-- Simon Riggs www.2ndQuadrant.comPostgreSQL Development, 24x7 Support, Training and Services