You should perform a formal assessment of your existing and planned resources and virtualization needs before acquiring a virtualization solution. Capacity planning determines how VMs will be distributed across physical computers for best performance and ease of management.
Your assessment should address the following questions:
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How many servers do you have?
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Which roles do they serve: application, database, web, and so on?
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How many servers do you need?
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How many users do you serve?
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Are you experiencing any issues with your current servers?
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Do you want to streamline any processes?
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Which server utilization trends do you observe?
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What percentage of your resources are underutilized and for how long, on average?
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Which usage patterns would you prefer to see?
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How much of your existing infrastructure can you virtualize?
Resource evaluation
In a non-virtualized environment, business applications are run on specific server hardware that consume computing and power resources even if the applications are idle. However, server virtualization solutions increase resource utilization through pooling, sharing, and clustering on an as-needed basis. Server consolidation also reduces operational and ownership costs while providing more streamlined and centralized management.
During your evaluation, a key factor is determining the number of users who'll use your virtualization solution. This influences hardware processing speed and ability, which is significantly less demanding for 80 to 100 users versus 8,000 to 10,000 on the same system. Network traffic to and from your virtualized server site is also a crucial factor, especially over the long term. You need to ensure your solution is flexible and responsive to changing business needs and a potentially increasing user base.
Component inventory
Prior to the availability of virtualization technologies, businesses usually had to operate separate servers for incompatible platform-specific applications, which could double the amount of server hardware. With virtualization, a single moderately powered server can run multiple, non-heterogeneous operating systems simultaneously, supporting a variety of business applications.
Inventory your current IT infrastructure with the goal of reducing, reusing, and repurposing or retiring existing server platforms. Consider the following while completing your inventory:
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How can virtualization better economize resource utilization or business operations?
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How might I better arrange separate physical server roles into a virtual server?
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Which applications or processes create unnecessary doubling-up or are otherwise wasteful of resources?
Tip: To repurpose an existing server for virtualization, ensure it meets all requirements for the virtualization software you intend to use.
Performance metrics
Performance data is another important element in the process of identifying the appropriate hardware for your virtualization solution. You need to gather performance metrics from your servers, storage systems, and networking gear over a period of at least 30 days. Monitor your applications and servers through normal business processes, and then determine the peaks and valleys of application use, and the types and quantity of resources these applications are using.
During the planning phase, you should determine which hardware and software to virtualize. Servers that make good candidates for virtualization generally are:
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Older servers (those with processors slower than 1 GHz [gigahertz]), to avoid upgrade costs.
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Infrequently used servers, to consolidate resources.
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Multiprocessor servers dedicated to single-processor applications, to optimize server resources.
Tip: Consider the environment in which your servers are used. For example, servers running in a production environment often have different requirements than those running in a development or test environment.
Most applications are candidates for virtualization because they use only a small percentage of available resources. The following are types of applications that you should consider virtualizing:
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Any application in a development or test environment
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Applications using a single processor
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Applications with low use rates
Note: Applications that exceed a single host server's available resources aren't good candidates for virtualization and should remain on a dedicated server.
Depending on the nature and complexity of your environment, you might need to hire an IT professional or consultant who can advise you and oversee the evaluation, selection, and deployment process for you. However, even if you decide to perform the work in-house, consider reviewing your evaluation results and preliminary virtualization software selection with resellers and experts. Spending $200 to $300 in consulting fees during the planning stage can potentially save many hours and thousands of dollars correcting otherwise avoidable miscalculations and mistakes.
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