Re: [CI] Query

[Ramachandra P. <lin...@ya...>]

Bruce,

Well I am working on clustering aspects of
EVMS(Enterprise Volume management system).

As part of volume management startegy we have to make
sure that every node in the cluster having concurrent
access to volumes and volume groups sees the same
state. This essentially leads to a requirement that
there is many to many communication between nodes.
(unless we have a master slave model; which I am
exploring).

The point here is everybody should see the same
sequence of messages, sent by anybody; for everybody
to build a consistent view of the system on all the
nodes.

For such a requirement, we could rely on techniques 
like globally ordered reliable messaging. 
Send-response trasactional model is also one of them,
but isn't it applicable only in master-slave kind of
scenarios?
I believe there are other techniques to accomplish the
same thing.

I wonder, if DLM also requires this feature; though I
am not positive.

Thanks,
Ram Pai

-- Bruce Walker <br...@ka...> wrote:
> Ram,
>   Thanks for the interest.
> We do not have specific support for global
> reliable ordered messaging.  The reason
> is that in all our years of SSI kernel
> clustering, we have rarely needed it.
> Algorithms that require talking to all nodes
> in the cluster do not scale well and we
> architectually avoid them whenever possible.
> 
> One exception to that is the Cluster Membership
> Service.  The current master node must step
> all the nodes through a couple of steps when
> nodes come up or down.  To do that, we tend to
> use the request/response (also knows as async
> RPC) feature of ICS.  Using the interface to the
> CLMS, a subsystem can determine the nodes to send
> a given message to.  He then can send them all
> (no interface in ICS to sendall so this is a call
> per node), and then wait for all the responses,
> after which he can go on to the the next phase.
> 
> Are there specific algorthims that you feel need
> this
> kind of capability.  If so, maybe we can discuss the
> need and maybe add this kind of capability.
> 
> bruce
> 
> > Hi,
> >     Trying to educate myself on CI. 
> > 
> >     Looking at the features published on the web
> page,
> > I did not find any support for global reliable
> ordered
> > messaging between nodes of the cluster. 
> > 
> >     How does any subsystem relying on CI make sure
> > that messages sent by any node in the cluster to
> > everybody else is seen in the same order on all
> the
> > nodes. Isn't this kind of feature neccessary for
> SSI
> > or any other clients of CI? If so how is that
> > accomplished?
> > 
> > 
> > Thanks,
> > Ram Pai 
> > 
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=====
Ram PaiIBM Corporation,Beaverton OR-...@ya... or pa...@us...

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