ServerNet Cluster Manual

ServerNet Cluster Description
ServerNet Cluster Manual—520575-003
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Benefits of Clustering
Benefits of Clustering
Clustering has multiple benefits. ServerNet clusters can improve:
•
Performance. For interprocessor communication, ServerNet clusters take
advantage of the NonStop Kernel message system for low message latencies, low
message processor costs, and high message throughput. The same message
system is used for interprocessor communication within the node and between
nodes. Furthermore, ServerNet clusters take advantage of the faster transmission
speed of ServerNet II for increased message throughput between nodes.
•
Availability. ServerNet clusters make it easier to repair or bypass problems by
diverting the load to other nodes.
•
Manageability. ServerNet clusters allow you to share resources easily. The
ServerNet cluster quick-disconnect capability makes it easier to implement planned
outages.
•
Scalability. ServerNet clusters provide an avenue for growth as your network load
increases.
ServerNet Cluster Terminology
This subsection introduces terms that are essential to understanding a ServerNet
cluster:
•
Cluster on page 1-12
•
Star Group on page 1-12
•
Node on page 1-13
•
Node Number on page 1-13
•
X and Y Fabrics on page 1-16
•
Internal ServerNet Fabrics on page 1-16
•
External ServerNet Fabrics on page 1-17
Cluster
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.
Star Group
A star group consists of an X and a Y cluster switch and up to eight connected
ServerNet nodes. This term is useful in describing the segments of a split-star or tri-
star topology. A split-star topology consists of two star groups connected by four-lane
links. A tri-star topology consists of three star groups connected by two-lane links.