mnesia growth limits

Sebastian Bello <>
Tue Jul 26 00:06:54 CEST 2005


Thank you very much!
    Sebastian-
----- Original Message ----- 
From: "Ulf Wiger" <>
To: <>
Sent: Monday, July 25, 2005 6:20 PM
Subject: Re: mnesia growth limits


> Den 2005-07-25 15:34:17 skrev Sebastian Bello <>:
> 
> > Hi all,
> >
> > some questions regarding a mnesia database growth:
> > 1- is there a limit in the number of records a database running on a  
> > single node can hold? How is this limit related to the individual  
> > tables' limits?
> 
> There isn't really a hard limit, unless all data resides in
> RAM. Then, mnesia is limited by the 4 GB address space in the
> current Erlang VM. Of course, this is not a limit on the
> number of records, but rather the total memory occupied by
> the table. I've personally had 10-20 million small objects
> in one node without problems, and others may have managed
> more.
> 
> There is no per-table limit. There is a configurable limit
> on the number of ETS tables allowed in the system. This is
> usually not a big problem for mnesia, as the default is
> ca 1400 tables.
> 
> 
> > 2- in a disk_copies database, how does the amount of memory affect  
> > mnesia's performance?
> 
> A disc_copies table keeps all objects both in RAM (ets tables)
> and on disk. Thus, for good performance, all objects should
> fit comfortably within physical memory.
> 
> However, with swapping enabled, things can work out reasonably
> well even if you exceed the physical memory, if a rather large
> portion of the data is only accessed very seldomly. Whether
> this holds for your applicaation is something you should
> explore through experimentation.
> 
> /Uffe
> 
> 





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