Availability Guide for Application Design

Overview of Server and Network Fault Tolerance
Availability Guide for Application Design—525637-004
2-6
Parallel Hardware Components
Normally, both fabrics or both buses are used for communication between processors.
If one fabric or bus fails, the operating system automatically reroutes all interprocessor
communication over the remaining fabric or bus.
Each K-series bus is controlled by its own controller, which is independent of the
processor logic. An S-series and NS-series ServerNet fabric is a complex web of
linkages also independent of the processor logic. A single processor failure, therefore,
cannot stop fabric or bus traffic between other processors.
Dual-Ported Controllers and ServerNet Adapters
An S-series or NS-series processor transfers data to I/O devices over a ServerNet
fabric. A K-series processor transfers data to I/O devices over an I/O channel.
Figure 2-3. NonStop Hardware Architecture, K-Series Server
Mirrored Disk
Processor
0
Processor
1
Processor
2
Disk
Controller
Disk
Controller
Disk
Disk
Disk
Controller
Disk
Controller
Disk
Disk
Multifunction
Controller
Dual Interprocessor Buses
Multiple
I/O
Channels
Mirrored Disk
I/O
Process
I/O
Process
I/O
Process
VST203.vsd