Configuring vSphere Distributed Power Management advanced settings to customize host power-on and power-off behavior

Products

• VMware vCenter Server

Issue/Introduction

Symptoms:

• vSphere Distributed Power Management (DPM) is enabled for a cluster but the hosts do not appear to power on when there is a high load or power off when there is a low load.
• Too many hosts are powered off at one time by DPM.

Environment

VMware vCenter Server 5.5.x
VMware vCenter Server 4.0.x
VMware vCenter Server 4.1.x
VMware vCenter Server 5.0.x
VMware vCenter Server 5.1.x

Cause

Resolution

These settings dictate how and when DPM attempts to power on or power off a host:

• DemandCapacityRatioTarget = the utilization target of an ESX/ESXi host. By default, this is set to 63%.
• DemandCapacityRatioToleranceHost = the range around the utilization target for a host. By default, this is set to 18%.

With these two parameters set at the default values, DPM attempts to keep the ESX/ESXi resource utilization between 45% and 81%. If CPU and memory utilization drops below 45% on all hosts, DPM attempts to power off a host. It can power off additional hosts until at least one host's CPU or memory utilization is above 45%. If CPU or memory utilization moves above 81% on all hosts, DPM attempts to power on a host to better distribute the load. DPM evaluates resource demand for calculating power-on operations over a five minute period. Resource demand for calculating power-off operations is calculated over a 40 minute period. The shorter evaluation period for power-on calculations helps to ensure a quick response to sudden resource demands. The longer evaluation period for power-off calculations helps to ensure that hosts are not powered off prematurely.

These additional parameters affect how many hosts are left powered on in a cluster:

• MinPoweredOnCpuCapacity = the lowest amount of powered-on CPU capacity that must be available. By default, this is set to 1 MHz.
• MinPoweredOnMemCapacity = the lowest amount of powered-on memory capacity that must be available. By default, this is set to 1 MB.

With these two parameters set at the default values, DPM is capable of powering off all but one host. HA admission control can help to keep additional hosts powered on but if HA is not in use these values must be modified such that more powered-on CPU and/or memory capacity is required to be available than one host can provide.

To change the range of CPU and memory utilization where DPM operates, add advanced settings corresponding to the desired DemandCapacityRatioTarget and DemandCapacityRatioToleranceHost values. The DemandCapacityRatioTarget can be set from 40% to 90%, while DemandCapacityRatioToleranceHost can be set from 10% to 40%.

For example, setting DemandCapacityRatioTarget to 50% and DemandCapacityRatioToleranceHost to 10% has the effect of DPM powering off a host (or hosts) when CPU and memory utilization drops below 40%. A host (or hosts) are powered on when CPU or memory utilization exceeds 60%.

To change how many hosts DPM is capable of powering off, add advanced settings corresponding to the desired MinPoweredOnCpuCapacity and/or MinPoweredOnMemCapacity values. The MinPoweredOnCpuCapacity and MinPoweredOnMemCapacity values are only limited by the total CPU and memory capacity of all hosts in the cluster.

For example, if there are three hosts in a cluster and each host has 48GB of memory and 24GHz of total CPU capacity, setting MinPoweredOnCpuCapacity to 24577 (1MHz more than 24GHz)or higher or setting MinPoweredOnMemCapacity to 49153 (1MB more than 48GB) or higher forces DPM to leave at least two hosts powered on.

To add advanced DPM settings:

1. In vSphere Client, right-click the cluster, then click Edit Settings > vSphere DRS.
2. Click Advanced Options.
3. Click in the area under the Options heading and enter the advanced parameter name.
4. Click in the area under the Value heading (to the right of the previously entered advanced option name) and enter the desired value.
5. Repeat until all necessary advanced parameters have been entered. Click OK.