Installation guide

C H A P T E R 1 2 VMware ESX Server Resource Management
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Memory Resource Management
VMware ESX Server provides dynamic control over the amount of physical memory
allocated to each virtual machine. You may overcommit memory, if you wish, so the
total size configured for all running virtual machines exceeds the total amount of
available physical memory. The system manages the allocation of memory to virtual
machines automatically based on allocation parameters and system load.
You may specify initial memory allocation values for a virtual machine in its
configuration file. You may also modify most memory allocation parameters
dynamically using the VMware Management Interface, the procfs interface on the
service console or the VMware Scripting API. Reasonable defaults are used
automatically when parameters are not specified explicitly.
You have access to information about current memory allocations and other status
information through the management interface, the procfs interface on the service
console and the VMware Scripting API.
For additional information on memory management by VMware ESX Server, see the
mem(8) man page. You may also view the abstract of a technical paper describing
memory resource management at www.usenix.org/events/osdi02/tech/
waldspurger.html.
If you have a server with NUMA architecture, be sure to see Using Your NUMA System
on page 418. Refer to the VMware ESX Server2 NUMA Support White Paper, available
at www.vmware.com/pdf/esx2_NUMA.pdf for information on supported NUMA
platforms.
Allocating Memory Resources
Three basic parameters control the allocation of memory resources to each virtual
machine:
• Its minimum size — min
The minimum size is a guaranteed lower bound on the amount of memory that
is allocated to the virtual machine, even when memory is overcommitted. The
system uses an admission control policy to enforce this guarantee. You cannot
power on a new virtual machine if there isn’t sufficient memory to reserve its
minimum size.
Set a virtual machine’s minimum for the minimal acceptable performance and
above the threshold where the guest operating system begins swapping
heavily. Use the performance monitoring tool of the guest operating system to
see if you are swapping. For more information on improving guest operating