[erlang-questions] Mnesia table replication scheme

Dan Gudmundsson <>
Tue Mar 1 21:10:40 CET 2016

You can mix as you want, if ram space is not a problem I would use
disc_copies on a two nodes.

tis 1 mar 2016 18:46 Khitai Pang <> skrev:

> Hi,
> I'm storing user accounts and organizations (a tree of users, i.e.
> departments, sub-departments, etc) in mnesia tables.  Modification to
> the data is not very frequent, i.e. not as frequent as a message queue.
> I can't afford losing the data.  Assume I have 9 erlang nodes (Linux VMs
> in a clound), and I haven't decided how many of them should be used for
> handling client connections and how many should be used for data
> storage/backup.
> I know that the more nodes a table is replicated on, the slower writing
> to it will be; I also know that ram copies are faster than disk copies;
> I am seeking to find a balance between performance and data safety.  How
> should the tables be replicated?  Should I use ram copies or disk copies
> or a hybrid scheme?  Can the data be in ram copies on some nodes and
> backed up in disk only copies on some other nodes?  If this is possible,
> will it provide performance as ram copies while still have data safety
> like disk copies?
> What is the best practice here?
> Thanks
> Khitai
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