Introduction

The primary motivation for this work comes from the recent growth in the energy usage of desktop computers. Recent studies estimate that PCs and monitors consume about 100TWh/year, out of which 65TWh/year is consumed by enterprise PCs. More statistics can be found in LBNL studies.

We have conducted our own measurements as part of this project, and found that many short idle periods exist (Figure 1), which are not exploited using usual power management mechanisms. User activity and background processes make it difficult for power management mechanisms to kick in. Though proxying can help, developing application layer proxies is cumbersome, and may cause some user disruption.

Figure 1

Approach: Exploit Virtualization

Our idea is to run the desktop in a virtual machine, and migrate it to a central server, when the VM (running the desktop) is idle. The original host is switched off to save energy. After the VM is migrated to the server, its memory is reduced to allow high consolidation of VMs. Figure 2 shows the architecture of our system.

Key challenges to realize this are

  1. How to determine idleness?
  2. How and when to migrate to server? How and when to migrate the VM back to its original host?
  3. How to reduce user disruption, when the VM is being migrated back?
Figure 2
See our USENIX ATC'10 paper for more details on how we solve these challenges.

Deployment

Efforts are underway at Microsoft Research to bring LiteGreen to enterprises. A small-scale deployment at MSR India show that LiteGreen can save up top 74% of energy compared to 32% with existing Windows and manual power management. A video showing the LiteGreen usage is available [Low res (8.1MB WMV), High res (28MB WMV)]. See this page for more details.

Figure 3

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