Setting up a cluster using direct connections between data nodes
requires specifying explicitly the crossover IP addresses of the
data nodes so connected in the
of the cluster
In the following example, we envision a cluster with at least
four hosts, one each for a management server, an SQL node, and
two data nodes. The cluster as a whole resides on the
172.23.72.* subnet of a LAN. In addition to
the usual network connections, the two data nodes are connected
directly using a standard crossover cable, and communicate with
one another directly using IP addresses in the
1.1.0.* address range as shown:
# Management Server [ndb_mgmd] Id=1 HostName=172.23.72.20 # SQL Node [mysqld] Id=2 HostName=172.23.72.21 # Data Nodes [ndbd] Id=3 HostName=172.23.72.22 [ndbd] Id=4 HostName=172.23.72.23 # TCP/IP Connections [tcp] NodeId1=3 NodeId2=4 HostName1=126.96.36.199 HostName2=188.8.131.52
The use of direct TCP connections between data nodes can improve the cluster's overall efficiency by enabling the data nodes to bypass an Ethernet device such as a switch, hub, or router, thus cutting down on the cluster's latency.
To take the best advantage of direct connections in this fashion with more than two data nodes, you must have a direct connection between each data node and every other data node in the same node group.