The support story for Microsoft products running on virtualization hardware is long and complicated. Until several years ago, Microsoft offered limited support for its flagship server products, such as SQL Server, Exchange Server, and SharePoint. Microsoft even left open the option that a support problem might need to be duplicated on physical hardware if support technicians couldn't determine the nature of the problem in a virtual environment. Adding to Microsoft's weak support story was the fact Virtual Server 2005 R2 was its virtualization product during the early days of Microsoft Office SharePoint Server (MOSS) 2007. Virtual Server 2005 R2 wasn't a hypervisor-based product and couldn't virtualize 64-bit guests, which limited supported environments to those running the 32-bit versions of MOSS 2007. This greatly curtailed the performance that could be achieved, particularly for the database role, which was the most resource-intensive and could take advantage of the 64-bit architecture the most. In addition, web front ends typically required significantly more memory than a 32-bit platform.
Two significant developments changed this story. The first was Microsoft's release of a 64-bit–capable hypervisor named Hyper-V. The second was the development of a program called the Server Virtualization Validation Program, which outlined Microsoft's official support stance on running its products on third-party hypervisor virtualization platforms. This program, outlined in the Microsoft article "Support policy for Microsoft software running in non-Microsoft hardware virtualization software" (support.microsoft.com/kb/897615), allowed for support of Microsoft products on third-party virtualization products that were validated by Microsoft and complied with certain criteria. These two developments opened the doors for Microsoft servers running on virtual machines (VMs) and gave peace of mind to organizations that needed to deploy supported virtualized solutions.
The 2007 wave of SharePoint products—which includes Windows SharePoint Services 3.0 (WSS 3.0) and MOSS 2007—was the first to gain broad virtualization support from Microsoft. However, in production, most organizations opt to virtualize only the web role and sometimes the query role. Other roles aren't typically implemented for various reasons. For example, the index role is often implemented only on physical hardware because of heavy processor and memory constraints and the limitation of one index server per Shared Services Provider.
Microsoft's official SharePoint 2010 support stance is that any SharePoint role or service is supported for hardware virtualization. SharePoint 2010 is positioned as a great version to virtualize because of the virtualization technology advances and reduction of disk I/O requirements for the indexing and search components. In addition, advances in hardware virtualization make it easier to virtualize I/O intensive applications such as SQL Server, allowing the SharePoint database role to be more easily virtualized. As a result, many organizations are looking at virtualizing their new SharePoint 2010 farms.