[erlang-questions] Mnesia cluster across OTP Releases

Dan Gudmundsson <>
Tue Dec 11 08:14:49 CET 2012


Yes should be possible except when I (and Ulf :-) mess things up, which we
did in mnesia-4.4.19.
In which mnesia couldn't talk to older versions.

I don't think that is not your problem here:
You have two different versions of the schema content here:
old:  {version,{{4,0},{'',{1355,182745,138103}}
new: {version,{{5,0},{'',{1355,182745,345805}}

Mnesia will not allow them to be merged, you have done something with the
table def before the merge.

/Dan


On Tue, Dec 11, 2012 at 1:12 AM, Daniel Dormont <>wrote:

> Hey gang,
>
> Is it possible and/or safe to run a Mnesia cluster across two Erlang
> nodes running different releases? In particular I have one node on
> R14B04 and another on R13B03, and when I tried to set up a cluster I
> got this rather nasty error:
>
> ** FATAL ** Failed to merge schema: Incompatible schema storage types
> (remote). on '' cs
>  [{name,schema},{type,set},{ram_copies,['
> ']},{disc_copies,['']}
>
>  ,{disc_only_copies,[]},{load_order,0},{access_mode,read_write},{index,[]},{snmp,[]},{local_content,false},{record_name,schema},
>
>  {attributes,[table,cstruct]},{user_properties,[]},{frag_properties,[]},{cookie,{{1351,554882,753639},'
> '}},
>  {version,{{4,0},{'',{1355,182745,138103}}}}],
>  on '' rcs
> [{name,schema},{type,set},{ram_copies,[]},{disc_copies,['
> ','']},
>
>  {disc_only_copies,[]},{load_order,0},{access_mode,read_write},{index,[]},{snmp,[]},{local_content,false},{record_name,schema},{attributes,[table,cstruct]},
>
>  {user_properties,[]},{frag_properties,[]},{cookie,{{1351,554882,753639},'
> '}},
>  {version,{{5,0},{'',{1355,182745,345805}}}}]
>
> But I wonder if there was something else wrong in my cluster
> configuration that caused this.
>
> thanks,
> Dan
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> 
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