NonStop S-Series Server Description Manual (G06.24+)

Introduction
HP NonStop S-Series Server Description Manual—520331-003
1-36
Maximum System With Single Server
Maximum System With Single Server
As shown previously in Figure 1-17 on page 1-33, five I/O enclosures can be
connected to the routers in the core tetrahedron. When more processor enclosures are
added to those of the core tetrahedron, those additional, outer processor enclosures
can each have four I/O enclosures.
With all processor enclosures added as shown in Figure 1-18, and with all I/O
enclosures connected, the configuration would be as shown in Figure 1-19. In this
case, 36 I/O enclosures can be supported.
ServerNet Clusters
Still referring to Figure 1-19, because no router ports in the core tetrahedron routers
are used for connection to I/O enclosures, the availability of these ports makes it
possible to interconnect multiple servers in a cluster. The clustering of servers permits
expansion of the overall system far beyond the limits of a single server. The remaining
topics in this section describe the various methods of clustering servers.
Just as the processors and I/O enclosures within a single server can have different
interconnection topologies, so also can the interconnection of clusters have different
topologies. Four such topologies are currently supported for ServerNet clusters:
•
Star topology
•
Split-star topology
•
Tri-star topology
•
Layered topology
The first three of these topologies are connective variations that are made possible by
the use of HP NonStop Cluster Switches (model 6770). The layered topology, which
provides the greatest extent of clustering capability, requires the use of HP NonStop
ServerNet Switches (model 6780). The two models of cluster switches cannot coexist
on the same external ServerNet fabric.
Note. A cluster is a collection of servers, or nodes, that can function either independently or
collectively as a processing unit. This use of “cluster” differs from the definition of a cluster in a
FOX ring. In a FOX ring, a cluster is synonymous with “server” and refers to a collection of
processors and I/O devices rather than a collection of servers.