From: Devananda
Date: August 24 2004 4:42pm
Subject: Re: Doubts about cluster features
List-Archive: http://lists.mysql.com/cluster/458
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Crouch, Luke H. wrote:

>you may specify any number (up to hundreds, I believe) of API nodes, which are typical mysql servers configured to use the cluster as their storage engine rather than their typical data files. in this way, you can have multiple mysql servers accepting connections and processing queries and all will have the same data. so you may round-robin or use some other method to balance your client connections to these servers and not worry about data consistency - it is handled by the cluster storage engine.
>  
>
I believe there is currently a limit of 64 nodes in the cluster, 
counting each DB node, each API node, and the MGM node. I remember 
reading that this was an arbitrary compile time limit, but I haven't 
heard how to change it. Please correct me if I'm wrong, or if anyone 
knows how to change this I would be quite interested :)

To help try and explain how the cluster functions, as it is quite 
different from traditional mysql or oracle databases,  I'll attempt a 
little ASCII art (wish me luck!)


                    -- any number of normal database clients --
       -- it makes no difference which API node a client connects to --
        [ Apache/php clients ]                     [ any other normal 
mysql clients ]
                             |                                          
               |
                          /  |  \                                       
            /  |  \
[ API nodes]  @ @  @         @      @            @     @  @  @

-- here's part of the magic of the cluster, all of the api nodes are 
connected to all of the DB nodes automatically --
-- thus load balancing is performed internally across all the DB nodes --
-- it's up to you (the dba/programmer) to load balance across the API 
nodes though --

[ DB nodes ]         D                 D                   D               D
                            (D)              (D)                 (D)   
         (D)               [ NoOfReplicas = 2, 3 or 4 ] -- this gives 
you a built in failsafe
                                                                         
                                 if one of the DB nodes crashes, it's 
replica automatically and
                                                                         
                                 almost seamlessly picks up its load

                                                    \  |  /
                                            [ MGM node ]
-- the MGM node must be aware of all API and DB nodes, since it is the 
central management process (does lots of stuff) --



I hope that helps :)

Devananda
Neopets, Inc