Mnesia and Oracle
Thu Aug 10 09:54:55 CEST 2006
What about my 50 gb data set?
What about my 100 gb data set?
Ultimately I think a major value is using mnesia as a coherent cache
and some SQL backend as a master storage.
On 8/10/06, Valentin Micic <> wrote:
> I do not think combining mnesia and MySQL is a good choice, no matter what
> justification one may put forward. If nothing else, it complicates
> maintenance, confuses people, and may (potentialy) compromise both
> products... not to mention a data integrity issues intrinsic to such an
> Mnesia's dets tables work reasonably well, even with huge data sets. The
> problem(s) starts when you start deleting records -- free list grows to the
> point that (IMHO) takes quite a long time to write it to disk. This becomes
> more obvious when one uses a lots of fragments. Thus, even if you shut the
> database regularly, it might corrupt few fragments. My guess: mensia
> controller does not give enough time to all dets processes (one per
> fragment) to flush their respective free lists to dist.
> A question for Erlang/OTP team: how can one prevent this from happening?
> I'm looking more (and more) to Berkeley DB for storage. Anybody, how does it
> compare to dets?
> ----- Original Message -----
> From: "Yariv Sadan" <>
> To: "Inswitch Solutions" <>
> Cc: <>
> Sent: Tuesday, August 08, 2006 11:51 PM
> Subject: Re: Mnesia and Oracle
> > Hi Eduardo,
> > I haven't had production experience with these databases, but there
> > are a couple of things I found by research that are keeping me from
> > using Mnesia exclusively in my application:
> > - Mnesia disc storage, based on dets, has a couple of drawbacks when
> > handling very large (many gigs) datasets: potentially long repair
> > times and memory consumption that grows with data fragmentation.
> > - QLC, the query engine for Mnesia, doesn't currently optimize joins.
> > If your queries involve joining big tables, they can take a long time
> > to execute.
> > The join optimizations are planned for a future R11 OTP release, but
> > there are no plans to change dets AFAIK.
> > Depending on your application, these issues may not be a big problem.
> > For the application I'm building, I'm planning on using both MySQL and
> > Mnesia, where MySQL will be used for storing high-volume data and
> > Mnesia for "live" session data.
> > Hope this helps!
> > Regards,
> > Yariv
> > On 8/8/06, Inswitch Solutions <> wrote:
> >> Hi,
> >> I'm already working with Oracle and Mnesia, and I'd like to hear
> >> experiences of the Erlang community about these databases.
> >> When deciding over Oracle or Mnesia database for an Erlang, or non
> >> Erlang, based real-time system which factors are in favour in one over
> >> the other (performance...?) ?.
> >> thanks, Eduardo
> >> Prepaid Expertise - Programmable Switches
> >> Powered by Ericsson Licensed Technology
> >> Eng. Eduardo Figoli - Development Center - IN Switch Solutions
> >> Inc.
> >> Headquarters - Miami-U.S.A. Tel: 1305-3578076 Fax: 1305-7686260
> >> Development Center - Montevideo - Uruguay Tel/Fax: 5982-7104457
> >> e-mail:
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