Introduction to Networking for NonStop S-Series Servers

Introduction to Networking for HP NonStop S-Series Servers—520670-005
5-1
5 Expand Network
The Expand subsystem enables you to connect as many as 255 geographically
dispersed HP servers to create a network with the reliability, capacity to preserve data
integrity, and potential for expansion of a single HP server.
This section provides a high-level overview of the Expand subsystem by describing the
following major features and capabilities:
•
Network Transparency on page 5-1
•
Multiple Communications Environments on page 5-4
•
Distributed Control on page 5-8
•
Automatic Message Routing on page 5-8
•
Fault-Tolerant Operation on page 5-9
•
Network Management on page 5-9
•
Online Expansion and Reconfiguration on page 5-11
•
Network Security on page 5-11
Network Transparency
To a user or an application, every server in an Expand network appears to be part of a
single server. When accessing a file or other resource on a server in an Expand
network, a user or an application does not need to know which route to take to reach
the destination or whether the destination is local or remote.
Interactive Access
When accessing a remote file or another resource interactively on an Expand network,
you use the same command or utility that you would normally use to perform the task
on your local server.
Programmatic Access
When accessing a file or another resource programmatically across an Expand
network, you use the same procedure calls you would use when writing a local
application. With a few exceptions, applications that were written to run in a local
environment can be used virtually unchanged in a network environment.
Expand Subsystem and the HP NonStop Kernel
The Expand subsystem is an extension of the NonStop Kernel operating system. You
can use the same methods for remote and local file access because the NonStop
Kernel and the Expand subsystem provide a uniform, message-based interface
between applications and operating system processes on different servers. The
message-based interface has two parts: the file system and the message system.
The size of the message sent between Expand processes is determined by many
factors.