[erlang-questions] Mnesia vs. ets+dets

Charles Hixson <>
Mon Nov 10 08:19:37 CET 2014

Sorry, something seems to have happened to what I originally sent. So 
this is essentially what got cut:

Those controls tell me what I needed to know about the original 
question.  Every 3 minutes to save seems reasonable, though I'd probably 
want to increase the number of allowed writes without flush to 100,000.  
But while looking things up I read some things that seemed to mean that 
Mnesia wanted to either hold the entire database in memory (disc_copies) 
or not hold any cache (disc_only_copies). This doesn't sound good, as 
what I need is a cache of active records in RAM.  I can still do this by 
using disc_only_copies and using it to fill an ets table which I 
occasionally flush to Mnesia, but this seems unexpectedly clumsy.  Am I 
reading the documentation incorrectly?  I really don't expect to be able 
to fit the entire table(s) into RAM.

On 11/09/2014 05:26 PM, Charles Hixson wrote:
> On 11/09/2014 12:56 PM, T Ty wrote:
>> I usually advocate using Mnesia because any schema you come up with 
>> you will later want some form of fault tolerance and as Joe Armstrong 
>> keeps harping, you can't do fault tolerance with one node.
>> ....
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