[erlang-questions] Mnesia: beyond the 2GB limit on 32bits arch

Igor Ribeiro Sucupira <>
Tue Jan 19 00:51:54 CET 2010


Hi, Zabrane.

If you are going to store 1.3 TB of data in a fragmented Mnesia
disc_only_copies table, I would recommend that you create AT LEAST
1024 fragments for your data (use a power of 2 for better distribution
of data among fragments). Each table fragment can hold up to 2 GB of
data, but the performance gets really bad way before you reach that
limit.

About table fragmentation in Mnesia:
http://www.trapexit.org/Mnesia_Table_Fragmentation

Depending on your performance requirements, you should think twice
(and run a lot of experiments) before you choose Mnesia to store
terabytes of data.

Good luck.
Igor.

On Mon, Jan 18, 2010 at 6:59 PM, zabrane Mikael <> wrote:
> Hi Igor,
>>
>> Are you planning to use disc_copies (you will need about 1.3 TB of RAM
>> on your cluster) or disc_only_copies tables?
>
> Reading speed isn't important for the moment. So "disc_only_copies" should
> be fine.
> Zabrane.

-- 
"The secret of joy in work is contained in one word - excellence. To
know how to do something well is to enjoy it." - Pearl S. Buck.


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