Understanding Virtual and Logical Processors

Understanding Virtual and Logical Processors

Q: What does "Virtual Processors per Logical Processor" mean?

A: Very often, when looking at virtualization and hypervisors, you see the phrase "Virtual Processors per Logical Processor" or it's written as "Virtual Processors:Logical Processor." What this refers to is that fact that virtual machines (VMs) are given a certain number of virtual processors, which use up resources on actual processor cores on the server (logical processors).

Virtual processors per logical processors relates to the number of supported virtual processors that should be created for each logical processor. Basically a ratio such as 8:1 means for each logical processor you have you should allocate only eight virtual processors on created VMs. If you had four logical processors in the server (i.e., a single processor with four processor cores), then you could allocate 32 virtual processors across VMs on that host.

This is often not a hard limit that's enforced but rather a supportability limit by the hypervisor vendor. Although Windows Server 2008 R2 Hyper-V had a 8:1 ratio for server workloads, there is no supportability limit in Windows Server 2012. If the workloads work in the environment, then the configuration is supported.

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