High Availability Software for the Intel® NetStructureTM ZT 4901 Technical Product Specification 11
Introduction 2
Intel® High Availability (HA) systems feature built-in redundancy for active system components
such as power supplies, system master processor boards, and system alarms. Redundant Host (RH)
systems are HA systems that feature an architecture allowing the Active Host system master
processor board to hand over control of its bus segment to a Standby Host system master processor
board.
This section gives an overview of the hardware and software used in systems supported by Intel’s
High Availability Software Development Kit (HASDK).
The following figure shows how the basic elements in an HASDK system are related.

2.1 Terminology

The following terms are commonly used in this document:
Active Host (also known as Current Host, owner, or bus segment owner)—A board is said to
be Active or the Active Host if it is providing System Host functions to the peripherals in a
CompactPCI backplane. This means that it is the Owner of at least one bus segment.
Figure 1. High-Availability CPU Architecture
CompactPCI
Interface
Controller
Slot
Driver
RH
Driver
Host
Application
Comm
Controller
Slot
Controller
Hardware
OS/Drivers Backplane
Driver
Hot Swap
Driver
RH
Driver
CompactPCI Bus
Current Host
Available Host
PCI-to-PCI
Bridge
RH Comm
Controller
RH
Comm
Driver
RH
Comm
Driver
RH Comm
Controller
Comm
Driver
Slot
Control
Driver
Host
Application
CompactPCI
Interface
Controller