Availability Guide for Application Design

Overview of Server and Network Fault Tolerance
Availability Guide for Application Design—525637-004
2-21
Use a Fault-Tolerant LAN
Use a Fault-Tolerant LAN
Redundant components provide the primary means for building a fault-tolerant LAN.
Several vendors offer products that can supply varying degrees of fault tolerance.
Figure 2-8 on page 2-22 shows the extra hardware and the connections for one PC
connecting to an S-series HP server.
In Figure 2-8, both primary and alternate LANs are in the same subnet, and both hubs
can see the traffic generated by the client processor. If a failure occurs on the primary
link, all traffic is routed through the alternate link and hub. The switchover occurs in the
client processor. All sessions are retained, and the switchover is invisible to the
application and the user.
This approach to configuring a fault-tolerant LAN requires the following hardware
components:
•
A dual-ported network adapter in the client processor
•
Dual paths and LAN hubs
•
Primary and backup E4SA or GESA ports (corresponding to parallel LAN
controllers in a K-series system) in the HP NonStop server system
Figure 2-7. K-Series Client/Server Architecture With a Continuously Available
Server
Processor 0
Processor 1
LAN
Controller
HP Server
System
Client
Processor
LAN
Card
Network Hub
VST207.vsd