[erlang-questions] Maximum number of Mnesia nodes

[denis]

Thanks Hakan for your response.

If I understand well, fragmented tables are interesting when we have high
volume of data. In my case, that's not the case, around 100000 records on 5
tables.
I plan to have one mnesia instance per server (and one server per machine),
each having each table in ram_copies replicated with the others servers.
Each server uses his local mnesia instance (maybe that's not the better
architecture?)

My concern is when for instance I do a delete or an insert into a table. The
transaction succeeds only when the insert or delete are done on each
replicated table. If I have only one server, the transaction time will be
for instance 10ms. If I have two server replicated, will it be 2*10ms ? For
N servers, what kind of factor can I expect? N, log(n), exp(N) ...?
I'm not sure that I can run 20 servers for instance, and keep good
performance, depending on the response time of the transaction commitment on
each node.

Thanks
Denis


> -----Message d'origine-----
> De : Hakan Mattsson [mailto:hakan@REDACTED]
> Envoyé : vendredi 27 juillet 2007 13:09
> À : denis
> Cc : 'David King'; 'Joel Reymont'; 'Erlang Questions'
> Objet : Re: [erlang-questions] Maximum number of Mnesia nodes
> 
> 
> The scalability of Mnesia depends heavily of your
> access patterns and how you have configured Mnesia.
> 
> If you ensure that the number of nodes involved in a
> typical transaction is constant, Mnesia should scale
> very well. One way of achieving linear scalability
> characteristics, is to use the concept called
> "foreign_key" in the chapter about fragmented
> tables. The bench example (mnesia/examples/bench)
> utilizes this technique.
> 
> When I wrote the "bench" benchmark example it turned
> out to scale almost perfectly linear. (By distributing
> the Mnesia tables over twice as many computers, the
> number of processed transactions per second also
> doubled.) But by that time I only had access to 10 (or
> was it 16?) identical computers, so I cannot say
> anything about how Mnesia scales beyond that. Worth to
> mentition is that I also did successfully run the bench
> example with fragmented tables distributed over all our
> machines at the office (50+). But as those computers
> had so different characteristics, it is impossible to
> say anything about the scalability. It was fun that it
> worked though.
> 
> Chandru, do you still have the highscore of the number
> of Mnesia nodes in a production environment?
> 
> /Håkan
> 
> On Fri, 27 Jul 2007, denis wrote:
> 
> > Date: Fri, 27 Jul 2007 11:15:18 -0400
> > From: denis <dloutrein.lists@REDACTED>
> > To: 'David King' <dking@REDACTED>, 'Joel Reymont'
> <joelr1@REDACTED>
> > Cc: 'Erlang Questions' <erlang-questions@REDACTED>
> > Subject: Re: [erlang-questions] Maximum number of Mnesia nodes
> >
> > Still nobody have a response for this?
> >
> > I'm in the case of designing a server embedding mnesia with ram_copies
> > tables. Several instances of the server can be launched, and the mnesia
> > tables are replicated.
> > I'm having the same concern with how many instances I can run before the
> > transaction committing in mnesia becomes a problem.
> >
> > If someone already used several replicated mnesia instances, I would
> like to
> > have some numbers.
> >
> > Thanks
> > Denis
> >
> > > -----Message d'origine-----
> > > De : erlang-questions-bounces@REDACTED [mailto:erlang-questions-
> > > bounces@REDACTED] De la part de David King
> > > Envoyé : lundi 23 juillet 2007 21:24
> > > À : Joel Reymont
> > > Cc : Erlang Questions
> > > Objet : Re: [erlang-questions] Maximum number of Mnesia nodes
> > >
> > > Did you ever get any off-list responses to this? I'm curious too.
> > >
> > > On 15 Jul 2007, at 05:44, Joel Reymont wrote:
> > >
> > > > Folks,
> > > >
> > > > How many Mnesia nodes are you running in your production
> > > > installation? I'm looking to find the maximum here.
> > > >
> > > > I'm only dealing with ram_copies tables (cache), trying to figure
> out
> > > > whether I can make every Yaws node a Mnesia node without slowing
> > > > transactions down too much.
> > > >
> > > > My current thinking is to wait and gather statistics before trying
> to
> > > > decouple Yaws and Mnesia . Still, I would love to know how much
> > > > transactions slow down with the addition of every new Mnesia node.
> > > >
> > > > 	Thanks, Joel
> > > >
> > > > --
> > > > http://topdog.cc      - EasyLanguage to C# compiler
> > > > http://wagerlabs.com  - Blog