What challenges exist with dynamic virtual machine failover?
The main technical challenges for performing a dynamic failover is that of allowing multiple physical hosts to share system state information. This includes the contents of memory. A true dynamic fail-over solution will provide a method of suspending operations on a particular VM and then transferring the contents of virtual memory to another host. successful, information related to the network configuration (virtual networks, MAC addresses, etc.) must be consistent. Often, the infrastructure to perform this task involves multiple machines connected by high-throughput, low-latency connections. You'll need to make sure that you have adequate reserved (i.e., unused resources) on the participating servers to make sure that they can maintain performance after a fail-over. Overall, there are numerous considerations that should be kept in mind. Performing "hot" fail-over operations are not impossible, but these environments take planning and maintenance.
This was first published in May 2007