[erlang-questions] [Q] Mnesia is overloaded

Dan Gudmundsson <>
Fri Sep 14 08:21:57 CEST 2007


Once in while (see mnesia dump_log_write_threshold, mnesia 
dump_log_time_threshold) mnesia dumps the transaction log, out to the
actual disc tables.
If a dump-process is not finished when the next starts it will write
the warning message.
I.e. it means that your are writing more to the disc than mnesia can 
handle, and if you continue to do it you will build up log files that
eventually will fill up all your disc space and that is not good.

So if you get these messages once in while during peek load it's no 
problem, if you continuously get them you have a problem you are 
overloading mnesia's disc performance.

/Dan

Ladislav Lenart wrote:
> Scott Lystig Fritchie wrote:
>>>>>>> "ll" == Ladislav Lenart <> writes:
>> ll> Mnesia is overloaded: {dump_log, write_threshold}
>>
>> Ladislav: This question appears frequently enough on this list that it
>> probably ought to become a member of the FAQ.  A search for that error
>> message in this list's archives should show several threads over the
>> last couple of years.
>>
>> Basic summary: it's a sign of a busy system and is mostly harmless.
> 
> Hello,
> 
> I've read the latest postings about it but I am still a little
> bit confused. For example what does "mostly harmless" from above
> mean?
> 
> Our mnesia database is now running on one node and is overloaded
> for ~20 concurrent writes which seems pretty low to me BTW. And
> what about ~1000 of them? How long will this report remain harmless?
> Or in other words, what is the maximum frequency of these concurrent
> bursts that mnesia running on one node can handle?
> 
> What is the main cause of the report? Is it a total number of
> concurrent writes? Or is it a total size of all data to be written
> (from all the writes)?
> 
> I am sorry to bother you all with this issue (again), but words
> like "often enough" and "mostly harmless" are too vague for me
> to be regarded as answers to my questions.
> 
> Thanks in advance,
> 
> Ladislav Lenart
> 
> 
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