Installation guide

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VMware ESX Server Administration Guide
Sizing Memory on the Server
These guidelines are intended to help system administrators determine an
appropriate amount of hardware memory for running a virtual machine workload on
ESX Server 2.1. Since the characteristics of your particular workload also influence
memory needs, you should follow up with testing to confirm that memory sizes
computed according to these guidelines achieve the desired results.
ESX Server uses a small amount of memory for its own virtualization layer, additional
memory for the service console and all remaining memory for running virtual
machines. The sections below explain each of these uses and provide a quantitative
sizing example.
Server Memory
ESX Server 2.1 uses approximately 24MB of system memory for its own virtualization
layer. This memory is allocated automatically when the ESX Server is loaded and is not
configurable.
Service Console Memory
The recommended amount of memory to configure for the service console varies
between 192MB and 512MB, depending on the number of virtual machines you plan
to run concurrently on the server:
• 192MB for <= 8 virtual machines
• 272MB for <= 16 virtual machines
• 384MB for <= 32 virtual machines
• 512MB for > 32 virtual machines
Virtual Machine Memory Pool
The remaining pool of system memory is used for running virtual machines. ESX
Server manages the allocation of this memory to virtual machines automatically
based on administrative parameters and system load. ESX Server also attempts to
keep some memory free at all times in order to handle dynamic allocation requests
efficiently. ESX Server sets this level at approximately 6 percent of the memory
available for running virtual machines.