Mnesia dB size limits

Dan Gudmundsson <>
Mon Sep 4 11:06:18 CEST 2006

I just want to point out that disc_copies don't use dets at all,
only disc_only_copies do.

disc_copies caches everything in ets though.


Scott Lystig Fritchie writes:
 > >>>>> "pr" == Philip Robinson <> writes:
 > pr> Damir asks:
 > >> What are the upper limits where system can still be called
 > >> "production quality" in terms of dB speed?
 > In a few months, a project I've been working on will go "live" with
 > approx 6GB total of data in about a half-dozen 'disc_copies' tables,
 > using both replication and fragmentation (though only on 2 machines,
 > but they have 16GB RAM each :-).
 > pr> When I wanted to retrieve a specific event there was no noticable
 > pr> delay, but most of my queries were for a date/time range.
 > It all depends on how the index(s) is defined and whether you were
 > using foldl/3 or index_match_object/3 or match_object/1 or
 > scary-but-works-quite-well-at-what-it-does select/2.
 > pr> I think the mnesia issues being mentioned on this list were to do
 > pr> with database recovery across nodes after a node failure...?
 > Step 0: Decide when to start the dead node.
 > Step 1: Start the dead node.
 > Step 2: There is no step 2.
 > Overall throughput can take a hit when starting a dead node, because
 > all out-of-date tables will be copied as-is from a live node.  So
 > doing Step 1 during your 1% or 5% peak usage time isn't a good idea.
 > Dealing with network partitions is trickier.  But if you're
 > clustering, then you've probably also got some kind of infrastructure
 > build for dealing with logging messages, events (of whatever sort,
 > including 'mnesia_down' events from Mnesia itself), alarms, etc
 > ... and all that makes it tricky enough to wuss out with an answer
 > like, "It depends."
 > -Scott

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