[erlang-questions] how: mnesia with simultaneous permanent node failure (EC2)

Paul Mineiro <>
Wed Dec 12 20:37:08 CET 2007


That sounds fine to me.

Another aspect of EC2 (as we plan to use it) is that the set of nodes in
use will change frequently (perhaps multiple times per day, in order to
save costs).  So it would be nice to allow abstract nodes with no
corresponding physical node.

Since my immediate problem is solved I have to move on, but I welcome any
changes to mnesia that make operating on EC2 easier.  Perhaps Amazon could
fund some work?

-- p


On Wed, 12 Dec 2007, Ulf Wiger (TN/EAB) wrote:

> Paul Mineiro skrev:
> > in order to get my disaster recovery situation managed on EC2, i went
> > ahead and wrote mnesia_schema:del_table_copies/2, which allows one to
> > remove multiple tables in one operation.
> [...]
> >>
> >> i'm thinking about using mnesia on EC2, but i'm having problems figuring
> >> out disaster recovery.
> >>
> >> some background: on EC2, you can start as many machines (instances) as you
> >> like.  if you lose one, you can start another, but it'll have a different
> >> hostname.  when you lose an instance, you lose whatever was stored on the
> >> drive.
>
> What if mnesia were equipped with a node name abstraction layer, and
> you could simply tell it which physical node corresponds to a given
> abstract node?
>
> This would also make it unnecessary to explicitly traverse backups
> in order to migrate a mnesia database from one machine to another;
> you'd simply re-map the abstract node name instead.
>
> BR,
> Ulf W
>

Optimism is an essential ingredient of innovation. How else can the
individual favor change over security?

  -- Robert Noyce



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