VMware vSphere 4 Technical Information download pdf (Page 35)

VMware, Inc. 35

This chapter provides guidance regarding resource management best practices. Most of the suggestions

included in this section can be implemented using the vSphere Client connected to a VMware vCenter server.

Some can also be implemented using the vSphere Client connected to an individual ESX host.

General Resource Management Best Practices

ESX provides several mechanisms to configure and adjust the allocation of CPU and memory resources for

virtual machines running within it. Resource management configurations can have a significant impact on

virtual machine performance.

This section lists resource management practices and configurations recommended by VMware for optimal

performance.

 If you expect frequent changes to the total available resources, use Shares, not Reservation, to allocate

resources fairly across virtual machines. If you use Shares and you upgrade the hardware, each virtual

machine stays at the same relative priority (keeps the same number of shares) even though each share

represents a larger amount of memory or CPU.

 Use Reservation to specify the minimum acceptable amount of CPU or memory, not the amount you

would like to have available. After all resource reservations have been met, ESX allocates the remaining

resources based on the number of shares and the resource limits configured for your virtual machine.

As indicated above, reservations can be used to specify the minimum CPU and memory reserved for each

virtual machine. In contrast to shares, the amount of concrete resources represented by a reservation does

not change when you change the environment, for example, by adding or removing virtual machines.

Don't set Reservation too high. A reservation that's too high can limit the number of virtual machines you

can power on in a resource pool, cluster, or host.

When specifying the reservations for virtual machines, always leave some headroom for memory

virtualization overhead and migration overhead. In a DRS-enabled cluster, reservations that fully commit

the capacity of the cluster or of individual hosts in the cluster can prevent DRS from migrating virtual

machines between hosts. As you move closer to fully reserving all capacity in the system, it also becomes

increasingly difficult to make changes to reservations and to the resource pool hierarchy without violating

admission control.

 Use resource pools for delegated resource management. To fully isolate a resource pool, make the

resource pool type Fixed and use Reservation and Limit.

 Group virtual machines for a multi-tier service into a resource pool. This allows resources to be assigned

for the service as a whole.

Virtual Infrastructure Management

1 2 ... 30 31 32 33 34 35 36 37 38 39 40 ... 53 54

No comments

VMware vSphere 4 Technical Information Page 35