Managing Serviceguard Eighteenth Edition, September 2010

Fibre Channel or HP StorageWorks XP or EMC Symmetrix disk technology can be
configured for failover among 16 nodes.
Note that a package that does not access data from a disk on a shared bus can be
configured to fail over to as many nodes as you have configured in the cluster (regardless
of disk technology). For instance, if a package only runs local executables, it can be
configured to failover to all nodes in the cluster that have local copies of those
executables, regardless of the type of disk connectivity.
Redundant Network Components
To eliminate single points of failure for networking, each subnet accessed by a cluster
node is required to have redundant network interfaces. Redundant cables are also
needed to protect against cable failures. Each interface card is connected to a different
cable, and the cables themselves are connected by a component such as a hub or a
bridge. This arrangement of physical cables connected to each other via a bridge or
concentrator or switch is known as a bridged net.
IP addresses can be associated with interfaces on a bridged net. An interface that has
an IP address associated with it is known as a primary interface, and an interface that
does not have an IP address associated with it is known as a standby interface. Standby
interfaces are those which are available for switching by Serviceguard if a failure occurs
on the primary. When Serviceguard detects a primary interface failure, it will switch
the IP addresses and any associated connections from the failed interface card to a
healthy standby interface card. In addition, if a LAN card fails on startup, or cannot
be detected because of other hardware failures, Serviceguard will effect a switch to a
standby if there is one available in the same bridged net.
Serviceguard supports a maximum of 30 network interfaces per node. For this purpose
an interface is defined as anything represented as a LAN interface in the output of
lanscan (1m), so the total of 30 can comprise any combination of physical LAN
ports, VLAN ports, IPoIB interfaces and APA aggregates. (A node can have more than
30 such interfaces, but only 30 can be part of the cluster configuration.)
A selection of network configurations is described further in the following sections.
See also “How the Network Manager Works ” (page 89). For detailed information
about supported network configurations, consult Hewlett-Packard support.
38 Understanding Serviceguard Hardware Configurations