Guiding Principles

The HA architecture design follows a number of guiding principles that drive the choice of the deployment type for the HA Add-On:

Aspect	Description
Cost	Consolidate applications components, use virtual environment for all components and leverage from existing infrastructure (compute/storage/network).
Performance	Have separate tiers for web/app/database, use load balance (when possible) and use physical servers.
Simplicity	Use a consistent solution across the system for ease of support, for example, Windows clustering.
Layering	No SPOF means layering redundancy at all levels (physical host, networking, hypervisor, OS, application services). This document focuses on application level redundancy and host failure.
SLA	Time to switch from active to standby should be minimal once a failure has been detected.