As recently reported on my blog we have managed to get MySQL Cluster CGE 6.3 to scale linearly with the addition of more nodes into the system.
In MySQL Cluster CGE 6.3 each node has a single thread handling most of
the work together with a set of file system threads.
In MySQL Cluster 7.0 the data nodes are now multithreaded. The design in
7.0 follows the very efficient design of 6.3 where each thread has absolutely no lock contention with other threads. All communication
between threads happens through messages. This means that scalability
of the data nodes is excellent. The single thread have been split into
up to four local data threads, one transaction handling threads,
and one socket communication thread plus the already existing file
system threads. With this set-up each data node can process 4.6X more
DBT2 transactions compared to 6.3.
This means that a 2-node cluster in 7.0 has the same performance as a
10-node cluster for 6.3 and a 4-node cluster similar performance to a
20-node cluster in 6.3. As earlier blogged each data node can handle
many hundreds of thousands of operations per second, so a cluster of
such nodes can handle many millions of operations per second.
The efficiency of the data node is such that one data node can handle
the traffic from a set of MySQL Servers residing on a 24-core MySQL
Server. So an example of a basic set-up for the MySQL Cluster 7.0 is
to use 2 8-core boxes with lots of memory and lots of disk bandwidth
for the data nodes. To use 2 24-core servers for the MySQL Servers that
mostly require CPU and networking bandwidth.
An important consideration for setting up a MySQL Cluster 7.0 is to
ensure that interrupts from the network stack doesn't kill performance
and also to have separate network infrastructure between the data
nodes in the cluster since it is very easy to overload the network
given the capabilities of the MySQL Cluster software.