This section discusses the decisions that are necessary when planning to install a Dolphin Express Interconnect.
Depending on the application that will run on the cluster, the choice of Dolphin Express Interconnect equipped machines differs.
For best performance, all machines that run either NDB or MySQL server processes should be interconnected with the Dolphin Express interconnect. Although it is possible to only equip a subset of the machines with Dolphin Express, doing so will introduce new bottlenecks.
Machines that serve as application servers (clients sending queries to MySQL servers processes) typically have little benefit of being part of the interconnect. Please analyze the individual scenario for a definitive recommendation.
Machines that serve as MySQL frontends (like to run the MySQL Cluster management daemon ndb_mgmd) do not benefit from the Dolphin Express interconnect.
Two nodes can be conneced directly using one or two CX4 cables, using PCI Express link width of x4 (single cable) or x8 (two cables). Three nodes can be connected directly using PCI Express link width x4. 1-10 nodes can be connected to a DXS410 switch (using x4, or x8 PCI Express link widths).
Generally, nodes that are to be equipped with Dolphin Express interconnect adapters should be placed close to each other to keep cable lengths short. This reduces costs and allows for better routing of the cables.
The maximum cable length is 10m for copper cables (CX4). For situations where nodes need to be placed in a significant distance, it is possible to use fiber instead of copper for the interconnect. Please ask your Dolphin sales representative for details.
Once you have decided on the physical node placement, the cables should be ordered in the according lengths. The Dolphin sales representative will assist you in selecting the right cable lengths.