Supervisor hierarchy question

Valentin Micic valentin@REDACTED
Tue Jan 25 08:32:16 CET 2005

How do we handle MNESIA backup? Hmmmm....
For our latest project, where we use MNESIA for some 90 million records, we
did develop a custom replication mechanism, that forwards the replication
data near-real time to MNESIA node that is NOT part of the same schema.
Whenever we want to do backup we:

1) Stop replication -- originating node keeps queuing changes
2) Stop a hot-stand-by database
3) Take a backup of data files
4) Start the hot-stand-by database
5) Start replication

When we need to restore, from scratch, we:

1) Create MNESIA schema
2) Start MNESIA
3) Create Database tables to mirror the original database
4) Stop MNESIA
5) Move backed-up data files
6) Start MNESIA

I'd be very interested in seeing similar approach in MNESIA proper, in
addition to existing replication mechanisms of course. How complicated would
it be to do that?


Has anybody used Polyserve products with MNESIA?
Is there any way to keep disk-based schema table information away form the
data files?
By the same token, is there a way for storing data-files belonging to the
same NODE using different disk volumes? I remember trying links a while ago,
but wasn't successful.

----- Original Message -----
From: "Mickael Remond" <mickael.remond@REDACTED>
Cc: <erlang-questions@REDACTED>
Sent: Friday, January 21, 2005 4:33 PM
Subject: Re: Supervisor hierarchy question

Torbjorn Tornkvist wrote:
> Yes, Nortel's SSL-VPN products is using Mnesia in all its glory.

Regarding Mnesia, I have a question to all of you that are also using it
in production. What do you use for backuping Mnesia ? What function do
you call ?
 From our experience, the Mnesia backup function can eat a lot of
memory. This is for sure related to the distributed feature and the fact
that a stable checkpoint must be generated.

But you need a lot of RAM to do such operation. This is the same for
table structure updates. On some hardware, it could be difficult to keep
several hundreds of Mo in RAM just to be safe with backups. Could this
be related to the number of waiting messages queued before Mnesia ?

So, I wanted to have your feedback on how you handle those
administration Mnesia process ?

Thank you in advance for your feedback.

Mickaël Rémond

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