> >
> > The thing is, we don't really care what the topology is. The only
> > requirement is that the session gets immediately deserialized once it
> > is replicated to other node, which should be either default or at
> > least configurable on most containers.
> >
> > So we let the container manage the replication topology. All we need
> > is to be notified when the session is replicated (pagemap
> > serialization and deserialization). All other approaches would require
> > container specific code.
>
> Yeah.. well. when node A fails over to node B and user clicks the back
> button is the end goal to handle that gracefully.  I was just suggesting
> a trivial way to accomplish the replication of the DiskPageStore's
> actual files.  This works around app container specifics for this point.
>
> Also you realize you responded to your own question asking about
> topology..

I do :), but you don't seem to quite realize the importance of knowing
the topology.

First of all, one DiskPageStore location was never supposed to be
shared across nodes and it will never work correctly that way. Each
node must have separate location where it's DiskPageStore stores the
files. Otherwise the result is pretty much unpredicable. This
basically rules out usage of replicated file system. Unless you
implement your own store probably with one file per page. We had such
implementation, the problem was that the performance didn't scale well
under load (lot of small writes).

As for the topology. In order to scale well with growing number of
nodes each node should be ideally backed by one other node.
Applications servers do this. The advantage of current DiskPageStore
implementation is that the DPS files are replicated to the exact node
that backs the session. So they are not just replicated all over the
cluster, which certainly wouldn't scale well.

-Matej

>
>
> ./C
>
>
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-- 
Resizable and reorderable grid components.
http://www.inmethod.com

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