Published: November 12, 2007   |   Updated: February 25, 2008

Before designing and implementing the infrastructure, determine which applications the infrastructure needs to support. This information will be used in later steps to determine resource requirements and, ultimately, to design the physical host infrastructure.

Task 1: Determine Application Compatibility

Although the goal of virtualization technology is to provide virtual environments that can support a wide variety of operating systems and applications, certain limitations can prevent some types of workloads from running virtualized. The first step in deciding which applications to virtualize is to consider the specific technical requirements for the application or operating system and map that against any constraints in the virtualization technology. Factors include:

• Processor architecture requirements.
• The number of required processors.
• Memory requirements.
• Graphics adapter requirements.
• Special hardware requirements.

Windows Server 2008 Hyper-V has the following constraints and limitations:

• Is available with Windows Server 2008.
• Requires specialized hardware chipset (Intel VT or AMD-V).
• No access to USB devices or hardware such as Host Bus Adapters (HBAs).

Virtual Server 2005 has the following constraints and limitations:

• Support for up to 3.6 gigabytes (GB) of virtual memory in each guest.
• Support for 32-bit applications.
• Support for a single virtual CPU.
• No access to USB devices or hardware such as Host Bus Adapters (HBAs).

Other technical considerations related to storage and networking are covered during steps 12 and 13 later in this guide. To ensure compatibility, IT staff members, users, and application support staff should verify applications by running them within a VM.

In addition to verifying technical compatibility, verify that the application vendor will support the application when used in a virtual workload. Also, consider the suitability of an application for virtualization. Security and/or other business requirements may lead an organization to run an application on physical hardware rather than virtually.

Task 2: Document the List of Applications

Most organizations run multiple operating systems, applications, and services that IT may consider moving to a virtual environment. To ensure that no important considerations are overlooked, a spreadsheet or table should be created that lists the applications, whether they are compatible with virtualization, and whether it is appropriate to virtualize them. Such a job aid could also include additional notes, requirements, and concerns. Filling out such a table can provide a very helpful structure to the process of planning for virtualization. Table 3 provides an example of information to include; the full table is shown in the appendix at the end of this document.

Table 3. Applications That Could Be Virtualized

This initial list serves as the basis for designing the virtualization infrastructure.

Validating with the Business

To ensure that the list of applications for virtualization is accurate, ask business stakeholders the following questions:

• Is the list of applications complete? The success of the virtual infrastructure design depends on determining requirements for applications that can be supported in a virtual environment.
• Are there applications on the list that should not be virtualized? It is often difficult to determine all the potential issues with virtualization based on technical details alone. The fact that a workload can be virtualized does not necessarily mean that it should be. Business leaders should understand the basic idea behind virtualization and should verify that it appears to be a suitable solution for each workload.
• Can the business accept the risks of moving to virtualization? Making changes to any application or server involves risk. The business should ensure that the level of risk is acceptable.
• Do specific legal requirements prevent an application from running within a VM? Requirements related to physical isolation of applications or that prevent certain applications from running on the same servers can prevent the use of virtualization. Another legal consideration is whether the application is licensed for use in a virtualized environment.
• Do support-related requirements prevent an application from being virtualized? Organizations should consider support contracts and associated technical requirements before committing to run an application within a VM.
• How should applications be prioritized? Businesses should prioritize applications based on importance.
• Do scheduling issues exist? Some applications may have availability requirements that prevent downtime during certain times of the year. If the time frame of the project is fixed, this may affect which applications are considered virtualization candidates.
• What about applications that are used only rarely? Applications that are rarely used might translate to a lower priority or might be removed entirely from the list of virtualized applications. Alternatively, they may prove excellent candidates since virtualization may offer a way to eliminate server hardware that runs all year, but is hardly ever used.
• Can business users assist in testing application compatibility? Although IT departments are responsible for deploying and supporting applications, business users are often experts in application functionality. Compatibility tests should involve input from representative users who can verify that their programs are running properly in the virtual environment.

Decision Summary

The list of applications considered for virtualization should begin with an analysis of the technical requirements of each operating system, application, and service. Good virtualization candidates are not only technically compatible with Windows Server 2008 Hyper-V or Virtual Server 2005, but also deliver business value and conform to business restrictions. The final list should include input from all affected users.

Additional Reading

·         Solution Accelerator for Consolidating and Migrating LOB Applications at https://www.microsoft.com/technet/solutionaccelerators/ucs/lob/lobsa/default.mspx provides information and details on moving workloads to a virtual environment.

·         Virtual Server 2005 Frequently Asked Questions at https://www.microsoft.com/windowsserversystem/virtualserver/evaluation/virtualizationfaq.mspx provides information on the features, capabilities, and limitations of Virtual Server 2005.