You can set up from one to six cluster interconnects in a cluster. While a single cluster interconnect reduces the number of adapter ports that is used for the private interconnect, it provides no redundancy and less availability. If a single interconnect fails, moreover, the cluster spends more time performing automatic recovery. Two or more cluster interconnects provide redundancy and scalability, and therefore higher availability, by avoiding a single point of failure.
In clustered environments, high-speed, low-latency interconnects and protocols for internode communications are essential. The SCI interconnect in Sun Cluster systems offers improved performance over typical network interface cards (NICs).
The RSM Reliable Datagram Transport (RSMRDT) driver consists of a driver that is built on top of the RSM API and a library that exports the RSMRDT-API interface. The driver provides enhanced Oracle Real Application Clusters performance. The driver also enhances load-balancing and high-availability (HA) functions by providing them directly inside the driver, making them available to the clients transparently.
The cluster interconnect consists of the following hardware components:
Adapters – The network interface cards that reside in each cluster host. A network adapter with multiple interfaces could become a single point of failure if the entire adapter fails.
Switches – The switches, also called junctions, that reside outside of the cluster hosts. Switches perform pass-through and switching functions to enable you to connect more than two hosts. In a two-host cluster, unless the adapter hardware requires switches, you do not need switches because the hosts can be directly connected to each other through redundant physical cables. Those redundant cables are connected to redundant adapters on each host. Configurations with three or more hosts require switches.
Cables – The physical connections that are placed between either two network adapters or an adapter and a switch.
Figure 3–4 shows how the three components are connected.