NonStop Systems Introduction

The NonStop Kernel
NonStop Systems Introduction—527825-001
6-10
Easy Transition to Distributed Processing
name, the operating system can determine the server’s actual physical location and
send messages from the requester to the server.
Disk drives, tape drives, and transaction entry devices (workstations, PCs, terminals,
and so forth) are all associated with I/O processes. The message system provides an
easy way for any requester process in the system to address and access any I/O
server process and use its devices.
Easy Transition to Distributed Processing
Because the operating system is message-based, almost any program that runs on a
local NonStop system will also run on a network of NonStop system. The only change
required in the application is the addition of node specifiers (system designations) to
the names of remote application processes, files, and devices that must be accessed.
In the NonStop system environment, the two worlds (the local world and the network)
are replaced by just one world: the world of messages. In this environment, a process
can send a message to a distant node almost as easily as it can to an adjacent local
processor in the same system.
This is why, with NonStop systems, the traditional leap from local processing to
distributed processing is hardly a leap at all. The operating system provides an
environment conducive to processor independence and to node independence, while
its message system is in place to facilitate cooperation among processors, processes,
and nodes.
The next two figures show how easily the processes running in a stand-alone system
can be distributed over the nodes of an Expand network.
In Figure 6-6 on page 6-10, processes running in a local NonStop system
communicate through the local message system. Messages are sent over the dual
ServerNet fabrics shown at the bottom of the figure.
Figure 6-6. Interprocess Communication in a Local System
Processor 0 Processor 1 Processor 2 Processor 3
Dual ServerNet fabrics
File system
Message system
P1
P2
File system
Message system
P3
P4
File system
Message system
P5
P6
File system
Message system
P7
P8
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