Installation guide

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VMware ESX Server Administration Guide
Configuring a Virtual Machine’s Memory and Virtual Processors
You can change how much memory to allocate to a virtual machine. You can also
review the amount of memory recommended by ESX Server, the maximum amount
of memory that can be allocated to the virtual machine and the maximum amount of
memory for smooth running of the virtual machine, given the number of virtual
processors.
Depending upon the guest operating system in the virtual machine and the number
of processors on the server, you can change the number of virtual processors it uses.
However, keep in mind the following:
• Virtual machines running certain guest operating systems, such as Windows NT,
can be configured with a single processor only. Review the list of supported
guest operating systems in the VMware ESX Server Installation Guide to see which
guests are multiprocessor- or SMP-capable.
• Virtual machines can be configured with multiple processors only if the server
has more than one processor. A virtual machine cannot have more virtual
processors than the server has physical processors.
• Multiprocessor-capable guest operating systems configured with a single
processor may require additional tuning if you increase the number of virtual
processors. At most, a virtual machine can have two virtual processors. For more
information, see Configuring a Virtual Machine to Use More than One Virtual
Processor on page 64.
• Multiprocessor-capable guest operating systems configured and tuned with
more than one virtual processor may not boot and will probably degrade the
performance of other virtual machines if you change the configuration to a
single processor. VMware recommends you do not downgrade a multiprocessor
virtual machine to uniprocessor.
Note: You can configure dual-virtual processor virtual machines only if you have
purchased the VMware Virtual SMP for ESX Server product. For more information on
this product, contact VMware, Inc. or your authorized sales representative.
To configure the virtual machine’s virtual processors and memory, complete the
following steps.