Configuration Considerations (ESX)

Configuration Considerations

Hardware

CPU

Feature	Set to	Intel name	AMD name
Node Interleaving	Disabled (allows NUMA operation)
Execute Protection	Enabled	eXecute Disable (XD)	No-Execute Page-Protection
Virtualisation assist	Enabled	Intel VT	AMD-V

CPU Power vs Performance

If in doubt put server BIOS settings to maximum performance - this ensures that ESX can get the most out of the hardware, allowing the BIOS to balance or use low power modes may impact VM performance. ESX's are expected to work hard, that's how they save you money, and so they should be set-up to be able to perform. In theory, allowing the motherboard to throttle back the CPUs when under low load shouldn't cause a problem.

When using ESX4.1 or higher then set the BIOS to allow the OS (ie ESX) control of CPU performance (if the setting is available), this allows the CPU Performance to be controlled dynamically by ESX as it manages VM load (and configurable through the VI Client).

See VM KB 1018206 - Poor virtual machine application performance may be caused by processor power management settings for further info

HP ASR

Should be disabled.

VMware don’t recommend that we use the HP ASR feature (designed to restart a server in the case of an OS hang), they’ve come across occasions when an ESX under load will suddenly restart due to ASR time-outs. See VM KB 1010842 - HP Automatic Server Recovery in a VMware ESX Environment for further info.

Networking

Beacon Probing

Should only be used when there are 3 or more physical NIC's assigned to the vSwitch, uplinked to the network switch.

This is to enable the ESX to be able to properly determine the state of the network during a faulty condition. If there's only two uplinks and the beacon gets lost between the two NIC's, then the ESX can't know which uplink is faulty, just that there is a fault.

See VM KB 1005577 - What is beacon probing? for further info.

Storage

ESX Installation Sizing

See VM KB 1026500 - Recommended disk or LUN sizes for VMware ESX/ESXi installations

SCSI Resets

When accessing centralised storage via SCSI, VMware recommends the following configuration (only the disabling of SCSI Device Resets is a change from the default). These settings are intended to limit the scope of SCSI Resets, and so reduce contention and overlapping of SCSI commands from different hosts accessing the same storage system.

• Disk.UseLunReset set to 1
• Disk.UseDeviceReset set to 0

Path Selection Policy (PSP)

• Active-Active (AA) - Storage array allows access to to LUN's through all paths simultaneously.
• Active-Passive (AP) - Storage array allows access to to LUN's through one storage processor at a time
• Asymmetric (ALUA) - Storage array prioritises paths available to access a LUN (See http://www.yellow-bricks.com/2009/09/29/whats-that-alua-exactly/)

Policy	For Arrays	Description
Most Recently Used (VMW_PSP_MRU)	All (default for AP arrays)	ESX uses whatever path is available, initially defaulting to last used or first detected at start up
Fixed (VMW_PSP_FIXED)	Active-Active (not for AP)	ESX uses preferred path, unless its not available. Can cause path thrashing with AP arrays
Fixed AP (VMW_PSP_FIXED_AP)	All (though really for ALUA)	As for Fixed, but the ESX picks the preferred path, and uses path-thrashing avoidance algorithm
Round Robin (VMW_PSP_RR)	All	ESX uses all available paths (will be limited by AP arrays)