NonStop Systems Introduction

NonStop Systems Introduction—527825-001
7-1
7 NonStop Server Architecture
The last section, Section 6, The NonStop Kernel, showed that the NonStop Kernel
supports the NonStop application server environment with a powerful, reliable
message system. The NonStop Kernel and its Expand network extension constitute
the software architecture of NonStop servers.
This section examines the hardware architecture of NonStop servers and considers
how this architecture supports the execution of programs in the NonStop application
environment.
Software and Hardware Views of Architecture
The next two figures compare the software and hardware architectures of NonStop
servers.
Figure 7-1 on page 7-1 illustrates the software architecture, as described in the last
section. Recall that, in each system, programs can run as process pairs (represented
by A and A', B and B', and so on). A process communicates with other local processes
and with local devices by using the file system and message system. A process
communicates with remote processes and devices in other systems by using the same
operating system layers and the Expand network software.
Figure 7-2 on page 7-2 now illustrates the hardware architecture of NonStop servers.
A NonStop server consists, first of all, of multiple processors that communicate with
each other over dual ServerNet fabrics. The choice of the word fabric is significant,
contrasting completely with the notion of a bus. Whereas a bus is conceived as a
straightline set of parallel conductors having a start point and an end point, a fabric is a
complex web of links between electronic routers that provide a large number of
possible paths from one point to another.
Figure 7-1. Software Architecture of NonStop Servers
Procesor 0 Processor 1 Processor 0 Processor 1
Dual ServerNet fabrics
File system
Message system
A
B'
File system
Message system
B
A'
File system
Message system
C'
D
File system
Message system
D'
C
Dual ServerNet fabrics
Expand
network
connection
System A System B
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