[erlang-questions] Mnesia

Gordon Guthrie <>
Wed Oct 14 09:25:33 CEST 2015


Mnesia is also a pain when it partitions - you have to write your own reconciliation programmes.

There has been a lot of work done on eventual consistency in *the other* Erlang database - Riak (disclaimer I am working at Basho now)

Riak implements eventual consistency - and post-partition self-healing using Consistent Replicated Data Types (or CRDTs) and the canonical set of standalone CRDT libraries is written in Erlang:
https://github.com/basho/riak_dt <https://github.com/basho/riak_dt>

There is a comprehensive reading list here:
https://christophermeiklejohn.com/crdt/2014/07/22/readings-in-crdts.html <https://christophermeiklejohn.com/crdt/2014/07/22/readings-in-crdts.html>

The combination of using Klarna’s (forthcoming) leveldb backend and a CRDT eventual consistency layer on top would be an interesting start offering a distributed transactional database with eventual consistency

Gordon

> On 14 Oct 2015, at 02:16, Richard A. O'Keefe <> wrote:
> 
> 
> On 14/10/2015, at 6:46 am, <> <> wrote:
>> 
>> I asked Fred what it would it take to upgrade Mnesia for the 21st century (or, at least, for the next decade). He didn't know.
> 
> There's one thing that strikes me.
> 
> I could go to a shop today and buy a 1 TB external drive for
> NZD 75, including Goods and Services Tax of 15%.  (At least
> that's what the ad I saw a couple of days ago said.)
> That's almost exactly USD 50.  This is a drive that fits in
> a shirt pocket, with room left over for all sorts of junk.
> 
> To make Mnesia a data base for the 2010s, it has to be able to
> handle at least 1TB of data.  Heck, I've got enough goodies-for-
> research money left that I could get the department to buy me
> ten of these gadgets, so let's say Mnesia
> - should be able to handle a single table in the low TB
> - should be able to handle a collection of tables in the
>   tens of TB
> - where "handle" includes creating, populating, checking,
>   recovering, and accessing in "a reasonable time".
> 
> That's a "single machine data base for the 2010s".
> Of course there are multicore, cluster, and network issues as
> well.
> 
> 
> 
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