Virtualization Best Practices - Choosing a Processor

As of this writing, Hyper-V provides support for up to 24 cores in the parent partition. A core is a unit of processing power. Both Intel and AMD have released processors that consist of multiple processor cores on a single processor. These processors plug into sockets on the computer’s motherboard. Having multiple processor cores on a single die allows even a single-socket system to execute multiple threads of execution at the same time. Although 24 cores sounds like a lot of processing power (and in most cases, it certainly is!), virtualization can easily use all of it.

You must consider three key factors about processors as you work through the planning stages:
• Number of processors in the system
• Number of cores on the processors in the system
• Speed of the processors in the system

Because one of the key features of virtualization is the ability to achieve higher density (running multiple VMs on a single physical host), administrators naturally gravitate toward the processor as a key bottleneck. After all, if a host runs out of processing power, those virtualized workloads may not be able to keep up with the demand being placed on them.

You need to answer a couple of key questions for the host:
• How many processors are necessary for this virtualization host?
• Do the processors need to provide t wo, four, or even six cores per processor?

The answer to these two questions is usually, “It depends.” Two schools of thought apply here, which bring up two more questions: Do you want to use more dual-socket systems, which usually have a lower price point? Or do you want to achieve maximum consolidation by going with quad-socket systems?

The price advantage of dual-socket systems is significant. At the time of writing, you can deploy three physical dual-socket systems for the price of one quad-socket system. You can then cluster those three dual-socket systems together in a high-availability configuration to ensure continuous uptime for the workloads running in the VMs. With the three-system configuration, however, you need to consider some other costs. Having three systems means further expenses for operating system licenses, management software licenses, and the administration of three servers. You also need to factor in the power costs of the three servers.

The other option, which uses only one quad-socket virtualization host, doesn’t provide any sort of backup or high availability—meaning that if the single host goes down, all the virtualized workloads will go down with it. But quad-socket servers generally provide a bit more in terms of expansion and I/O scalability, which could result in additional VMs being deployed on a single host.

Some enterprises are also considering the use of blade servers. Although the up-front cost of the enclosure is higher, the ability to use 14 systems in 7 units of rack space (for example) could be a better fit for some companies. As you can see, there’s no simple answer when you’re deciding on the best configuration for your host.

Source of Information : Sybex Windows Server 2008 Hyper-V Insiders Guide to Microsofts Hypervisor

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