6.0.1

vSphere HA has several advantages over traditional failover solutions:
Minimal setup
After a vSphere HA cluster is set up, all virtual machines in the cluster get
failover support without additional configuration.
Reduced hardware cost
and setup
The virtual machine acts as a portable container for the applications and it
can be moved among hosts. Administrators avoid duplicate configurations
on multiple machines. When you use vSphere HA, you must have sufficient
resources to fail over the number of hosts you want to protect with vSphere
HA. However, the vCenter Server system automatically manages resources
and configures clusters.
Increased application
availability
Any application running inside a virtual machine has access to increased
availability. Because the virtual machine can recover from hardware failure,
all applications that start at boot have increased availability without
increased computing needs, even if the application is not itself a clustered
application. By monitoring and responding to VMware Tools heartbeats and
restarting nonresponsive virtual machines, it protects against guest operating
system crashes.
DRS and vMotion
integration
If a host fails and virtual machines are restarted on other hosts, DRS can
provide migration recommendations or migrate virtual machines for
balanced resource allocation. If one or both of the source and destination
hosts of a migration fail, vSphere HA can help recover from that failure.
vSphere Fault Tolerance Provides Continuous Availability
vSphere HA provides a base level of protection for your virtual machines by restarting virtual machines in
the event of a host failure. vSphere Fault Tolerance provides a higher level of availability, allowing users to
protect any virtual machine from a host failure with no loss of data, transactions, or connections.
Fault Tolerance provides continuous availability by ensuring that the states of the Primary and Secondary
VMs are identical at any point in the instruction execution of the virtual machine.
If either the host running the Primary VM or the host running the Secondary VM fails, an immediate and
transparent failover occurs. The functioning ESXi host seamlessly becomes the Primary VM host without
losing network connections or in-progress transactions. With transparent failover, there is no data loss and
network connections are maintained. After a transparent failover occurs, a new Secondary VM is respawned
and redundancy is re-established. The entire process is transparent and fully automated and occurs even if
vCenter Server is unavailable.
Chapter 1 Business Continuity and Minimizing Downtime
VMware, Inc. 11