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Using VDI to compound cost and power consumption savings

A virtual desktop infrastructure can reduce power consumption and compound the savings realized from server consolidation. This tip indicates how one company reaped the benefits of VDI.

In 2007, server consolidation solidified its importance as one of the most compelling drivers for server virtualization. Virtualization has yielded substantial consolidation ratios -- reducing the number of servers required, the amount of floor space needed, and the amount of power and cooling needed -- generating significant ongoing savings. For many, consolidating on blade servers compounds savings even further, by reducing per-server floor space footprint and per-server power requirements. But can extending virtualization to desktops through a virtual desktop infrastructure yield even greater savings than consolidating servers with server virtualization?

For IT organizations with large user populations that are well suited to virtual desktops, the answer can be a resounding yes. For these organizations, moving all or portions of their user base to a virtual desktop infrastructure can deliver similar reductions in the number of physical computers and the corresponding power requirements.

Hear Barb Goldworm speak at one of our virtualization seminars.

Real-world power savings?
After achieving success with VMware Virtual Infrastructure 3 (VI3) last year, one IT organization shifted a significant portion of users from physical desktops to virtual desktops using VMware's Virtual Desktop Infrastructure (VDI) and plans to move the remainder next year. As a result, the company has reduced power consumption requirements for its desktops at the same order of magnitude as its server consolidation efforts, which reduced a server farm from roughly 200 physical IBM servers to 200 virtual servers running on 14 IBM IBM BladeCenter servers. Total power consumption for servers decreased from approximately 60,000 watts (or 300 watts per server) to 4,500 watts (or 23 watts per virtual server): a total savings of more than 90%.

Building on this success, the organization's desktop virtualization project converted from roughly 800 physical IBM desktops to 800 virtual desktops running on 14 IBM BladeCenter servers, accessed via thin clients. Power consumption for total desktop delivery (including thin-client devices but excluding monitors, which were constant) went from approximately 80,000 watts total (or 100 watts per desktop) to 17,000 watts total (or 20 watts per virtual desktop), with a total savings of almost 80%.

In addition to power consumption savings, moving to a virtual client model offers other benefits. Because applications and data are all centrally located rather than dispersed on desktops or laptops where theft is an issue, virtual desktop infrastructure can improve security. The model also simplifies remote technical assistance, because desktops are under central control, with well-managed golden images. And availability is improved, with all automated failover and high-availability capabilities that come with an overall virtual infrastructure -- in this case, including the features of VMware High Availability (HA) and VMotion-- as well as the failover capabilities inherent in BladeCenter architecture.

There are some caveats, however, as far as conversion to virtual desktops. Moving desktops to VDI requires that the virtual-client virtual machines (VMs) use storage on a storage area network, which can add up quickly. Thorough planning and testing for optimum configurations of things like hard-disk space and memory allocation become essential prior to a large-scale rollout.

So if you're exploring power and cooling as part of a server consolidation project, don't forget desktop virtualization . Although power reduction may not be the primary reason to implement a virtual desktop approach, it offers additional benefits for those undertaking blades and consolidating servers. A virtual desktop solution isn't the right answer for every company or set of users, but for those that are a good fit for a VM, there are significant benefits.

About the author: Barb Goldworm is the president of and chief analyst at Focus Consulting, a consulting firm specializing in systems, software and storage. Goldworm has spent the past 30 years in various technical, marketing, senior management and industry analyst positions with IBM, Novell, StorageTek, Enterprise Management Associates and several startups. She can be reached at

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