Consider these tips when you set up your communications paths.
- Be sure you have adequate bandwidth on your communication lines to handle
the non-cluster activity along with the clustering heartbeating function and
continue to monitor for increased activity.
- For best reliability, do not configure a single communication path linking
one or more nodes.
- Do not overburden the line that is responsible for ensuring that you are
still communicating with a node.
- Eliminate as many single points of failure as possible such as having
two communication lines coming into a single adapter, same input-output processor
(IOP), or same tower.
- If you have an extremely high volume of data being passed over your communication
lines, you may want to consider putting data replication and heartbeat monitoring
on separate networks.
- If you are using Internet Protocol (IP) multicast, you should see the
TCP/IP Configuration and Reference for multicast restrictions that may apply
to different types of physical media.
- User Datagram Protocol (UDP) multicast is the preferred protocol that
the cluster communications infrastructure uses to send cluster management
information between nodes in a cluster. When the physical media supports multicast
capabilities, cluster communications utilizes the UDP multicast to send management
messaging from a given node to all local cluster nodes that support the same
subnet address. Messages that are sent to nodes on remote networks are always
sent using UDP point-to-point capabilities. Cluster communications does not
rely on routing capability for multicast messages.
- The multicast traffic that supports cluster management messaging tends
to fluctuate by nature. Depending on the number of nodes on a given LAN (that
supports a common subnet address) and the complexity of the cluster management
structure that is chosen by the cluster administrator, cluster related multicast
packets can easily exceed 40 packets per second. Fluctuations of this nature
can have a negative impact on older networking equipment. One example is
congestion problems on devices on the LAN that serve as Simple Network
Management Protocol (SNMP) agents that need to evaluate every UDP multicast
packet. Some of the earlier networking equipment does not have adequate bandwidth
to keep up with this type of traffic. You need to ensure that you or the network
administrator has reviewed the capacity of the networks to handle UDP multicast
traffic to make certain that clustering does not have a negative impact on
the performance of the networks.