Virtualization is one of the most exciting technologies in the computer industry at the moment.  The reason for this is quite simple.  Most servers run at a very low level of resource utilization.  Virtualization allows companies to consolidate physical servers into virtual ones thus reducing their overall hardware expenditures and simplifying overall system administration.  This article will focus on one of the aspect of simplifying system administration, that being high-availability.

High-availability is the holy grail for the system administrator.  Aside from answering the obvious questions of what happens in case of a physical failure, an event that should happen very infrequently, it also helps solve the more common issue of how to get a scheduled outage window to perform  system maintenance.  As companies increasingly automate business processes getting these outage windows becomes proportional more difficult due to business costs associated with system unavailability.

In the video above I demonstrate how to use the VMWare Server in a clustered environment.  More important than simple failover of a VM from one node to another is the ability to save state on one node and to restart it on another node.  To put this in English, any applications that were running on the VM on one node will still be running on the other node when it's brought back up.

Below is a list of the commands I used in the video:

                vmware-cmd d:\testvm\testvm.vmx start

                vmware-cmd d:\testvm\testvm.vmx suspend

                cluster group vm /moveto:sclabent11

In the demo above I simply used Notepad as my application to demonstrate the saving of state and failover.    One of my next projects will be to build out a complete ERP system, Oracle’s OneWorld, on VMs and test how well real applications failover.

Please let me know any thoughts or questions you may have on the topic of virtualization and high-availability.