Virtualization cost savings come from reduced labor, less server maintenance and even your licensing model. But...
virtualization technology licensing comes in many forms and is ever-changing, so I've broken down a few Microsoft licensing models. With Windows Server licensing and SQL Server licensing, you can cut virtualization costs using a per-processor licensing model.
Cutting costs with the Windows Server licensing model
For most environments, Windows Server is the predominant server operating system. Windows Server 2003 is still popular in data centers in spite of Windows Server 2008's release and R2 enhancements that are now in finished product form.
For Windows server operating systems, the Datacenter Edition per-processor licensing model.provides virtualization cost savings. Windows Server Datacenter edition offers unlimited virtualization rights. This Windows Server licensing model effectively states that for each processor that is licensed for Windows Server Datacenter Edition, an unlimited number of Windows Server operating systems can be run on those processors.
The default application is to have Hyper-V as the virtualization engine with the unlimited number of Microsoft Server operating systems, but it's not required. This means that organizations can run Citrix XenServer or VMware-based virtualization on processors licensed with Windows Server Datacenter Edition. Not placing vendor limits allows for more virtualization cost savings.
For most situations, this allows all Windows Server editions to be run as well. This makes many version issues go away because the unlimited virtualization rights apply to all Windows Server versions (2008, 2003, 2000, etc.) and editions (Enterprise, Standard, Advanced, etc.). For virtualized data centers, being able to fulfill any operating system requirement with no additional OS costs is an agility factor that can benefit larger installations through some significant virtualization cost savings.
Virtualization cost savings with the SQL Server licensing model
Per-processor licensing can also extend to a Microsoft SQL Server licensing model. The per-processor licensing model for SQL Server instances has a high cost of entry investment but can pay dividends if a high number of database servers are required.
When a processor is licensed for SQL Enterprise Edition, that processor can contain any number of SQL instances above it. For VMware installations in large IT environments, a popular practice is to create a cluster designated for SQL Server workloads.
The cluster would have each processor licensed for SQL Server Enterprise Edition, Windows Server Datacenter Edition and vSphere Enterprise Plus Edition. At face value, this is an expensive proposition. If focusing on SQL Server licensing alone, the entry costs to create an environment with unlimited SQL rights have a high price.
For environments with a very large SQL footprint, this licensing model can be an attractive option for a number of reasons. The foremost of these is the additional security options that go with a no-cost -- in terms of SQL engine and operating system licensing costs -- option to separate various database engines at the OS level. Another benefit is that by designating hosts for SQL Server VMs, it can be easier to provision higher-tiered storage to these hosts for potentially more critical workloads.
The jump to a per-processor licensing model may not make sense for all situations. But if a large number of new server instances are expected, then the jump may make sense -- especially if you're considering Windows Server licensing or SQL Server licensing. It is important to work scenarios out where the licensing model investments are not wasted and the upgrades can be complicated.
About the expert
Rick Vanover (firstname.lastname@example.org) has the vExpert, VCP, MCITP, MCTS and MCSA certifications. He is an IT Infrastructure Manager for Alliance Data in Columbus, Ohio and is an IT veteran that specializes in virtualization, server hardware, operating system support and technology management. Follow Rick on Twitter @RickVanover.