PLANNING

We’re going to begin by introducing vSphere 5’s availability options (all of which were also available in vSphere 4, but which have been upgraded to a greater or lesser degree). Some options are fairly reactive and/or manual in nature, while others are more proactive and automatic. After we provide a brief overview of the options, we’ll cover the HA and FT options individually. Each option involves trade-offs and costs, and they can be used in any combination to provide more robust solutions and notifications.

Alarms versus HA versus FT versus DR

vSphere includes four different options for providing varying levels of high availability, as listed in Table 12.2.

HA

HA requires some careful thought and planning to work well. It works out of the box, but with a little time spent optimizing it, it can be even better. This section will cover why HA exists, the basic architecture of HA, and how HA handles various failures that could occur. Our goal for HA in this book is to discuss the design and implementation of HA for typical scenarios for most administrators. For an in-depth review of the subject by two experts in HA (and employees of VMware), refer to VMware vSphere 5 Clustering Technical Deepdive by Frank Denneman and Duncan Epping.