I have a confession.
My data center kit has been using too much energy.
Having kit available at my disposable is great, but I have been wasting this resource when it's not required by my workloads. And if there's one thing I try to be conscious of, it's energy consumption. Just ask my kids who I chase from room to room turning off lights, screens, and the lot when they aren't using them.
But why not in the data center? Did you know that hosts typically use 60%+ of their peak power when idle?
Until recently, I had overlooked configuring my kit to use the vSphere Distributed Power Management ("DPM") feature to manage power consumption and save energy.
With the release of vSphere 6.0 it's a good time to review and take deeper look into the capabilities and benefits of this feature.
What is VMware vSphere Distributed Power Management?
VMware vSphere Distributed Power Management is a feature included with vSphere Enterprise and Enterprise Plus editions that dynamically optimizes cluster power consumption based on workload demands. When host CPU and memory resources are lightly used, DPM recommends the evacuation of workloads and powers-off of ESXi hosts. When CPU or memory resource utilization increases for workloads or additional host resources are required, DPM powers on a required set of hosts back online to meet the demand of HA or other workload-specific contraints by executing vSphere Distributed Resource Scheduler ("DRS") in a "what-if" mode. DRS will ensure host power recommendations are consistent with the cluster constraints and resources being managed by the cluster.
Beneath the covers there are key challenges that DPM addresses to enable effective power-savings capabilities:
- Accurately Assessing Workload Resource Demand
- Avoiding Frequent Power-on/Power-off of Host and Excessive vMotion Operations
- Rapid Response to Workload Demand and Performance Requirements
- Appropriate Host Selection for Power-on/Power-Off within Tolerable Host Utilization Ratios
- Intelligent Redistribution of Workloads After Host Power-on/Power-Off
Once DPM determines the number of hosts needed to satisfy all workloads and relevant constraints, and DRS has distributed virtual machines across hosts to maintain resource allocation constraints and objectives, each powered-on host is free to handle its power management
Hosts Entering and Exiting Standby
When a host is powered-off by DPM, they are marked in vCenter Server in "standby" mode indicating that they are powered-off but available to be powered-on when required. The host icon is updated with a crescent moon overlay symbolizing a "sleeping" state for the host.
DPM can awaken hosts from the standby mode using one of three power management options:
- Intelligent Platform Management Interface (IPMI)
- Hewlett Packard Integrated Lights-Out (iLO), or
- Wake-On-LAN (WOL).
Each protocol requires its own hardware support and configuration. If a host does not support any of these protocols it cannot be put into standby by DPM. If a host supports multiple protocols, they are used in the following order: IPMI, iLO, WOL. This article is focused on the use of the first two.