[Fedora-directory-users] Five-way MMR

[Kimmo Koivisto]

Hello

I have five servers with FDS 1.0.4 and I would like to use multimaster 
replication in those servers.

I know that there is some kind of limit for the number of servers in MMR,   
four servers is the maximun if I remember correctly.

So, can I add replication agreements to five servers, is there a hardcoded 
limit for four servers or what? What happends if I add those agreements?

Regards,
Kimmo Koivisto

[Rich Megginson]

Kimmo Koivisto wrote:
> Hello
>
> I have five servers with FDS 1.0.4 and I would like to use multimaster 
> replication in those servers.
>
> I know that there is some kind of limit for the number of servers in MMR,   
> four servers is the maximun if I remember correctly.
>
> So, can I add replication agreements to five servers, is there a hardcoded 
> limit for four servers or what? What happends if I add those agreements?

There is no hard coded limit.  4 is the number of masters we have tested 
extensively with.  The MMR protocol supports a theoretical limit of 
65000+ masters, but we've never actually tested with that many :-)   The 
practical limit is the number of threads, since each replication 
agreement is a separate thread within the server process.  So at some 
point you will see performance degradation, depending on what type of 
processors you have, how many you have, the amount of RAM, the size of 
your databases, and the transaction rate.

That being said, 5 masters should work.  Please let us know, if you try 
it, what your experience is, and some information about your replication 
topology.
> Regards,
> Kimmo Koivisto
>
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