Mikael Ronstrom wrote:
> First partition goes to first group, next partition to next group
> and so forth. Each partition is placed on all nodes in the node group it is placed.
I think Im still not quite getting this 100% :o)
My understanding was based on
http://dev.mysql.com/doc/refman/5.0/en/mysql-cluster-db-definition.html, which says:
"Node groups are formed implicitly. The first node group is formed by the set of data nodes with the lowest node IDs, the next node group by the set of the next lowest node identities, and so on".
I also believed that the number of partitions == number of node groups (http://dev.mysql.com/doc/refman/5.0/en/mysql-cluster-nodes-groups.html).
So for setting up node groups and partitions, the only variables I could see were:
a) The number of data nodes
b) The value of the NoOfReplicas parameter
Hence my example: If I have 4 data nodes (1, 2, 3, 4) and number of replicas == 2, I thought that nodes 1 and 2 would form the first group (partition "A") and nodes 3 and 4 would form the second group (partition "B"). Thus I thought that data would be partitioned across groups A and B, and replicated within them.
Likewise, If I have 2 data nodes (1, 2) and number of replicas == 2, I thought that nodes 1 and 2 would form the first and only group (partition "A"). Thus I thought that data would be replicated across nodes 1 and 2, but not partitioned.
So I guess Im not getting something, as my understanding does not tally with your comment:
> Actually the number of partitions is equal to the number of data nodes.
Could you possibly elaborate to help me clear up my confusion?
Many thanks,
Dave