Supervisor hierarchy question

Ulf Wiger (AL/EAB) <>
Wed Jan 19 09:50:32 CET 2005


> BTW: I've been asked the other day why did I choose a Disney 
> (a.k.a. Mickey Mouse) Database for implementation of some
> serious data volumes. They said, Even Ericsson is not using
> MNESIA... not that we have any problems, but...

I guess it depends on what you mean by 'serious data volumes'.
The biggest mnesia database that I have is roughly 1 GB of 
data in about 6 million objects. It works like a charm.
Traditionally, this wouldn't qualify as 'serious data volumes',
but I think it's a bit more than most people think 
Mnesia is capable of handling.

That Ericsson wouldn't be using Mnesia is rubbish! We use it
extensively in our Erlang-based applications, and these 
apps have very high reliability requirements.

However, if you refer to e.g. large provisioning databases, 
then no, we don't use Mnesia for those applications. There 
are many reasons for this, but that Mnesia would not be good 
enough is not really one of the main reasons. Having 
said that, though, I think making Mnesia a serious contender
in that niche would require a tremendous amount of work,
mainly as regards feature set, support tools, etc, as well
as incorporating another disk-based backend, like Berkeley
DB. It might also involve introducing a lot of compromises
that would make Mnesia a less attractive realtime DBMS.

> 
> How does one fight such (IMHO) unjustified argument(s)? Can 
> anybody tell me of any comercial application of MNESIA.

In general, I think just about all commercial Erlang-based 
products use Mnesia one way or another. The Synapse Automatic
Device Configuration tool uses Mnesia with a Berkeley DB backend,
if I'm not mistaken, and handles quite large data volumes.

I think part of this discussion should be the aspect of support.
If you have a commercial product with high reliability 
requirements, you would want premium support from whatever 
database vendor you choose. Erlang/OTP offers premium support,
but I can't tell you whether they are willing to do it for
the type of application you're intending (because (1) I don't
work at OTP, and (2) I don't know what the app is.) If they 
are willing to support you, you have little to fear. If your
application differs too much from what Mnesia was designed for,
OTP will probably not offer any guarantees. That's not to say
it wouldn't work; just that it would be unsupported, just as 
if you would download mysql from the net, build it from source
and use it in your application. It probably works very well,
but if it doesn't, you're on your own.

For many of the applications dealing with vasts amounts of 
important data, the support factor is key to which DBMS they
choose. That, and the licensing model (esp. if it's subscriber
data.)

/Uffe

> 
> Valentin.
> 
> 
> ----- Original Message -----
> From: "Eric Merritt" <>
> To: "Torbjorn Tornkvist" <>
> Cc: <>
> Sent: Wednesday, January 19, 2005 12:25 AM
> Subject: Re: Supervisor hierarchy question
> 
> 
> > Torbjorn,
> >
> >  You can always use the ODBC stuff provided with the erlang/OTP
> > distribution. I needed something a little closer to the 
> wire and with
> > a few extra options. Thats the main reson I implemented my own.
> > Otherwise, the erlang ODBC stuff works just fine.
> >
> >
> > On Tue, 18 Jan 2005 23:19:51 +0100, Torbjorn Tornkvist
> > <> wrote:
> > > Eric Merritt wrote:
> > >
> > > >Parts of it would. The connection pool specific stuff 
> would work just
> > > >fine. However, my connection directly implements 
> postgresql's version
> > > >3 protocol so it wouldn't be able to speak to mysql. However, if
> > > >someone is willing to implement the mysql protocol I am more then
> > > >happy to work with them to develop a consistant api.
> > > >
> > > >
> > > Ok, I don't know (yet) what that protocol consist of, but 
> I think it
> > > could be of interest to be able to access mysql from Erlang.
> > > Any pointers where to look ? I guess I should browse around
> > > mysql.com... ;-)
> > >
> > > Cheers, Tobbe
> > >
> > > >
> > > >On Tue, 19 Apr 2005 00:30:55 +0200, Torbjorn Tornkvist
> > > ><> wrote:
> > > >
> > > >
> > > >>Would this code work with mysql as well ?
> > > >>
> > > >>Cheers, Tobbe
> > > >>
> > > >>Eric Merritt wrote:
> > > >>
> > > >>
> > > >>
> > > >>>That would actually rock. Its part of a larger 
> codebase that I havn't
> > > >>>decided whether or not to open up. However, I have no 
> problem at all
> > > >>>opening up the postgresql stuff. If you would like I 
> will grant you
> > > >>>access to the subversion repository.  If you can't get 
> a subversion
> > > >>>client I will post it on the web somewhere. I don't 
> actually expect
> to
> > > >>>get the driver to a usable state before the end of the week.
> > > >>>
> > > >>>
> > > >>>On Tue, 18 Jan 2005 15:48:06 +0000, 
> > > >>><> wrote:
> > > >>>
> > > >>>
> > > >>>
> > > >>>
> > > >>>>Hi Eric,
> > > >>>>
> > > >>>>I read the message about creating a client for 
> postgresql in erlang.
> I am interested in helping you out, as I use postgresql from 
> erlang and
> would be interested in such an interface. Can you post the 
> code? I can help
> you test it if you'd like.
> > > >>>>
> > > >>>>Thanks
> > > >>>>Ernie
> > > >>>>
> > > >>>>
> > > >>>>
> > > >>>>
> > > >>>>
> > > >>>
> > > >>>
> > > >>>
> > > >>>
> > > >>
> > > >>
> > > >
> > > >
> > > >
> > > >
> > >
> > >
> >
> >
> > --
> > I'm a programmer, I don't have to spell correctly; I just have to
> > spell consistently
> 
> 



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