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

In this step, begin to design the host infrastructure based on workload requirements collected in the preceding steps. The goal of step 7 is to determine the most appropriate type of host hardware on which to deploy the VMs. In making the selection, take account of the prerequisites for the virtualization platform, whether Windows Server 2008 Hyper-V or Virtual Server 2005 R2 SP1. The characteristics of each option also depend on the organization’s current and planned hardware investments.

Note   Form factor here refers to CPU and RAM. Later sections in this guide discuss disk space and network requirements.

Option 1: Use Existing Hardware

In many cases, organizations already have host hardware resources that can be reconfigured and redeployed to support the virtual workload. For example, in a server-consolidation scenario, the goal is to increase overall hardware use by combining workloads onto fewer physical host computers.

These machines can differ significantly based on the age of the hardware, the system specifications, and other capabilities. Often, using existing hardware can decrease overall costs of implementing a virtual infrastructure (cost avoidance) but may result in sacrificing standardization. The primary drawback for using existing machines is that the hardware configuration might not match the “ideal” configurations for the host system.

Option 2: Purchase New Hardware

When purchasing new hardware, the organization has the opportunity to set a hardware configuration standard that can be used throughout the company. In some cases, organizations can acquire already-approved server form factors. In other cases, considering newer server specifications that provide increased scalability is more appropriate. Organizations should be prepared to complete significant evaluation and performance testing of host hardware platforms before making significant investments. Considerations include the following:

• Scaling up versus scaling out. Fewer servers with large memory and CPU support can be easier to manage and can be more cost-efficient for some infrastructures. Using smaller, commodity servers with lower capacity can involve a smaller capital outlay but often requires additional management effort.
• Fault tolerance features. The hardware configuration for new servers should support fault tolerance and fault tolerance features based on application requirements.
• Hardware management features. Organizations should consider purchasing servers that support the online addition of components such as network adapters and memory to reduce downtime and simplify administration.

It may be necessary to review this step and the defined strategy when applications are actually allocated to each system. It is not uncommon to iterate several times through form factor decisions to find the optimal configuration.

Evaluating the Characteristics

The following tables compare the characteristics of the options.

Validating with the Business

Ask the following questions to verify that the host hardware approach meets the organization’s business requirements and directions:

• What is the total budget for implementing the virtual infrastructure? Details help define options for purchasing and deploying new hardware. Budget constraints might necessitate changes to the list of applications that can be supported in the virtual infrastructure.
• Are the hardware estimates aligned with purchasing goals? Factoring in current and future purchasing decisions is a necessary step in designing the virtual infrastructure.
• Will the business realize the cost reductions and savings it anticipates? Often, Total Cost of Ownership (TCO) and Return on Investment (ROI) numbers must be calculated to ensure that the organization will achieve the expected benefits.

Decision Summary

Determining the optimal hardware configuration for the virtual infrastructure should involve an inventory of existing host hardware systems. Compare resource specifications to the requirements summarized in step 6 to determine whether new purchases will be required or would be optimal. Business constraints play a crucial role in determining the most appropriate approach for the organization.