Marathon Technologies on Virtualization and High Availability

Ping and pray, I like that ;-)

But protecting virtual environments from unplanned downtime is a different matter. In many cases, virtual environments employ traditional clustering and failover techniques, which use rudimentary heartbeat pings to check the status of a virtual machine. This approach suffers from several drawbacks:

• Clustering and failover add cost and complexity to the environment, requiring manual configuration, setup, scripting and testing to define the appropriate actions to take in case of failures. This additional administrative complexity can introduce errors, contributing to availability issues.
• Heartbeat pings are unable to reliably determine the health of a virtual machine and may not distinguish between I/O path failures, server failures, and lack of system resource. In some cases, these limitations may result in unnecessary or false failovers. In other cases, discrete storage or network device outages are not identified as failures and the system does not fail over.
• The failover process is far from certain; it assumes that the administrator has configured the standby system appropriately for the application and has maintained that configuration. If the target system is not configured appropriately, then when a failover does occur, the application or virtual machine is inoperable on the standby system, causing a "failed failover." Given the sense of uncertainty, some refer to this approach as "ping and pray."

Link at Virtual Strategy Mag