VMware vSphere 4 Technical Information download pdf (Page 17)

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This chapter provides guidance regarding ESX software itself and the virtual machines that run in it.

ESX General Considerations

This subsection provides guidance regarding a number of general performance considerations in ESX.

 Plan the deployment. Allocate enough resources, especially (in the case of ESX, but not ESXi) for the

service console.

Table 2-1 lists symptoms of insufficient resources for the service console.

 Allocate only as much virtual hardware as required for each virtual machine. Provisioning a virtual

machine with more resources than it requires can, in some cases, reduce the performance of that virtual

machine as well as other virtual machines sharing the same host.

 Disconnect or disable unused or unnecessary physical hardware devices, such as:

 COM ports

 LPT ports

 USB controllers

 Floppy drives

 Optical drives (that is, CD or DVD drives)

 Network interfaces

 Storage controllers

Disabling hardware devices (typically done in BIOS) can free interrupt resources. Additionally, some

devices, such as USB controllers, operate on a polling scheme that consumes extra CPU resources. Lastly,

some PCI devices reserve blocks of memory, making that memory unavailable to ESX.

 Unused or unnecessary virtual hardware devices can impact performance and should be disabled.

For example, windows guests poll optical drives (that is, CD or DVD drives) quite frequently. When

virtual machines are configured to use a physical drive, and multiple guests simultaneously try to access

that drive, performance could suffer. This can be reduced by configuring the virtual machines to use ISO

images instead of physical drives, and can be avoided entirely by disabling optical drives in virtual

machines when the devices are not needed.

ESX and Virtual Machines

Table 2-1. Symptoms of Insufficient Resources for the ESX Service Console

Insufficient Resource Type Symptoms

Memory Poor response from the vSphere Client

Disk Space Inability to write diagnostic messages to log; inability to log into the service

console

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VMware vSphere 4 Technical Information Page 17