Even before design of
began in 1996, it was evident that one of the major problems to be
encountered in building parallel databases would be communication
between the nodes in the network. For this reason,
NDBCLUSTER was designed from the very
beginning to permit the use of a number of different data
transport mechanisms. In this Manual, we use the term
transporter for these.
The MySQL Cluster codebase provides for four different transporters:
TCP/IP using 100 Mbps or gigabit Ethernet, as discussed in Section 18.104.22.168, “MySQL Cluster TCP/IP Connections”.
Direct (machine-to-machine) TCP/IP; although this transporter uses the same TCP/IP protocol as mentioned in the previous item, it requires setting up the hardware differently and is configured differently as well. For this reason, it is considered a separate transport mechanism for MySQL Cluster. See Section 22.214.171.124, “MySQL Cluster TCP/IP Connections Using Direct Connections”, for details.
Shared memory (SHM). For more information about SHM, see Section 126.96.36.199, “MySQL Cluster Shared-Memory Connections”.Note
SHM is considered experimental only, and is not officially supported.
Scalable Coherent Interface (SCI), as described in the next section of this chapter, Section 188.8.131.52, “SCI Transport Connections in MySQL Cluster”.
Most users today employ TCP/IP over Ethernet because it is ubiquitous. TCP/IP is also by far the best-tested transporter for use with MySQL Cluster.
We are working to make sure that communication with the ndbd process is made in “chunks” that are as large as possible because this benefits all types of data transmission.
For users who desire it, it is also possible to use cluster interconnects to enhance performance even further. There are two ways to achieve this: Either a custom transporter can be designed to handle this case, or you can use socket implementations that bypass the TCP/IP stack to one extent or another. We have experimented with both of these techniques using the SCI (Scalable Coherent Interface) technology developed by Dolphin Interconnect Solutions.