6.7

VMware uses the following terminology. Understanding these terms can help you plan your strategy for
CPU resource allocation.
CPU The CPU, or processor, is the component of a computer system that
performs the tasks required for computer applications to run. The CPU is
the primary element that performs the computer functions. CPUs contain
cores.
CPU Socket A CPU socket is a physical connector on a computer motherboard that
connects to a single physical CPU. Some motherboards have multiple
sockets and can connect multiple multicore processors (CPUs).
Core A core contains a unit containing an L1 cache and functional units needed
to run applications. Cores can independently run applications or threads.
One or more cores can exist on a single CPU.
Resource sharing Shares specify the relative priority or importance of a virtual machine or
resource pool. If a virtual machine has twice as many shares of a resource
as another virtual machine, it is entitled to consume twice as much of that
resource when the two virtual machines are competing for resources.
Resource allocation You can change CPU resource allocation settings, such as shares,
reservation, and limit, when available resource capacity does not meet
demands. For example, if at year end, the workload on accounting
increases, you can increase the accounting resource pool reserve.
vSphere Virtual
Symmetric
Multiprocessing (Virtual
SMP)
Virtual SMP or vSphere Virtual Symmetric Multiprocessing is a feature that
enables a single virtual machine to have multiple processors.
Virtual CPU Limitations
The maximum number of virtual CPUs that you can assign to a virtual machine is 128. The number of
virtual CPUs depends on the number of logical CPUs on the host, and the type of guest operating system
that is installed on the virtual machine.
Be aware of the following limitations:
n
A virtual machine cannot have more virtual CPUs than the number of logical cores on the host. The
number of logical cores is equal to the number of physical cores if hyperthreading is disabled or two
times that number if hyperthreading is enabled.
n
Not every guest operating system supports Virtual SMP, and guest operating systems that support
this functionality might support fewer processors than are available on the host. For information about
Virtual SMP support, see the VMware Compatibility Guide at
http://www.vmware.com/resources/compatibility.
vSphere Virtual Machine Administration
VMware, Inc. 88