August 04, 2008, 2:17 PM — Judging by blogs and associated discussions on CIO.com, many industry pundits and those investigating virtualization don't fully understand the direct costs associated with using virtualization software; specifically when they choose not to use enhancement tools such as VMware vMotion, VMware SVMotion, VMware HA and DRS.
In one sense they're not absolute requirements: it's possible to manage a virtual infrastructure without them; they may not be necessary in every environment.
But not using them can increase your own costs and the level of your risk.
Even considering the relatively high price of some of these options, using them will increase the stability and uptime of your virtualized systems in the long run.
Take VMware's vMotion as an example: Without vMotion, if you needed to work on a physical host for virtualized servers, you would need to turn off/shutdown all VMs, fast-migrate them to another host, and then boot them on the new host.
In general, your minimal downtime would be the length of time it takes to reboot a virtualized server (on average we could safely say this will be roughly three to five minutes per VM. With 50 VMs this adds up quickly.) However, since this is a reboot of the server, all this activity would have to happen after regular business hours or be scheduled during non-critical times.
After-hours work comes with a cost premium, mainly from overtime and comp time and other considerations for the staff involved. The cost of vendor hardware technicians or technical support is higher after hours than during normal hours of operation in your area of the world.
With vMotion it is possible to save costs by doing this work during normal business hours, eliminating both the added costs and scheduling issues involved with off-hours migrations.
VMware's SVMotion can save the same kinds of costs for the same reasons when a SAN or iSCSI server firmware needs to be upgraded. Rather than shutting anything down or keeping staff working late, you can just do the work during normal operating hours.
VMware HA automates failover of hosts so that there is no need to have extended downtimes while VMware DRS employs vMotion to move VMs to hosts with more unused capacity. Now tie in VMware DPM (Distributed Power Management), which is experimental but not for long, it is even possible to shutdown hosts on off hours, saving on power costs.
In addition, these tools will allow you to minimize downtime which could cost you penalties for not meeting your Service Level Agreements.
Before nay-saying the use of these tools, sum up the costs and see if you will benefit from them. Compare the cost of buying, learning and implementing the tools to the amount of downtime, overtime, after-hours support and power costs you can save by using them.
