New York City's Saint Vincent Catholic Medical Centers is saving power and money by replacing its desktop computers with thin clients running virtualized operating systems.

Saint Vincent's has virtualized more than 600 desktops so far, said Chris Hansen, the system architect for the hospital network. Eventually, it will replace all 5,000 desktop PCs with thin-client devices.

Pano Logic supplies the thin clients. The OSes -- all Windows XP at present -- are streamed from a VMware ESX virtualization platform.

By using thin clients rather than full-featured PCs, the hospital system could save US$170,000 a year in electricity costs, Hansen estimated. Although additional power would be consumed by the servers to run the virtualized OSes, and by the storage arrays to house user data, running 600 thin clients would still consume only a quarter of the power required to run 600 desktop computers, he said.

The hospital is conducting operational tests to get an even better estimate of the power savings.

While server virtualization is all but mainstream by now, desktop virtualization has remained on the fringe of corporate IT for several years. Analysts are optimistic that it may become more widely adopted in the year to come, thanks to pressures from thinner budgets, soaring electricity bills and the growing complexities of desktop client management. If so, Saint Vincent's is on the cutting edge of this trend.

Saint Vincent's runs numerous medical facilities in and around New York City, with St. Vincent's Hospital Manhattan, founded in 1849, being the anchor for the institution.

The hospital is no stranger to virtualization. It has already virtualized most of its servers, consolidating 300 physical servers into 6 hosts, first using VMware's ESX 3.5, and now VMware VSphere 4.0.

With success on the server side, Saint Vincent's looked at virtualizing the desktops. Its employee desktops are nearly a decade old, many still running Windows 2000. But rather than embarking on a hospitalwide refresh, the IT team first compared the costs of purchasing new PCs with the cost for thin clients.

Most thin-client technologies use a form of VDI (Virtual Desktop Infrastructure), in which the entire desktop is streamed from a server. With this setup, the desktop is replaced by a thin-client device, which streams its OS and applications from a server. A PC can consume an average of 100 watts or more while in operation, whereas a thin-client device will consume less than 10 watts.

In the hospital's price comparison, the cost of procuring thin-client devices and support servers turned out to be about the same as buying PCs, Hansen said. However, the savings in electricity costs from thin clients would be considerable.

"We found that the power consumption was going to be dramatically lower with VDI," Hansen said

For Saint Vincent's, power costs are no small issue. The hospital is one of the largest users of power in the city and is looking to cut consumption wherever possible. And since the hospital has been hit with budget woes of late, trimming operational costs anywhere possible has become a necessity.

Once settled on a thin-client approach, the hospital IT team looked at a number of thin-client platforms. They settled on Pano Logic because of its simple footprint. The thin-client device itself is a small, square box, which can be affixed directly to the back of an LCD monitor. The unit also has outputs for Ethernet, audio and video, as well as a couple of USB jacks.

"Our endpoint device has no processor, no OS, no drivers. There is nothing you need to install, nothing you need to configure," explained Parmeet Chadda, an executive vice president at Pano Logic. "You plug it into your network and it is automatically discovered by the back-end."

The thin-client approach also helps in managing user OSes. Instead of each user getting an individual OS, a single master copy is copied across multiple virtual machines, which are streamed to clients. During the boot-up process, the OS is matched with the user's home directory.

"Users can't save anything locally on the virtual machine. Everything is redirected to the home drive, which is on a clustered file server," Hansen said.

The hospital system maintains a few workstations for specialized medical duties. But since most employees have the same basic requirements from their computers, only about six different OS images are actually needed to cover almost all use cases. Applications can be either packaged with the OS master image or streamed through VMware ThinApp software. So when an application or OS needs to be patched or updated, it can be done by updating the few master copies, rather than updating each employee computer individually.

For Saint Vincent's, one of the most valuable features of this setup may be how it facilitates user mobility -- something truly handy for doctors making the rounds. For instance, an employee can be working on one monitor at one location, sign out, go to another location, say in another building, and sign back in on another thin client. All the open documents and programs will still be on the virtual desktop, exactly where they were before the employee signed out at the other location.

Thin-client computing's reputation has long been dogged by criticism of sluggish performance, from the inherent lag in accessing resources over a network. Hansen said he hasn't noticed any performance degradation, however, especially compared to the older computers that the thin clients are replacing. The VMs are running on servers with much faster processors and larger allocations of memory than the old desktop computers had.

Each four-processor server, running either quad-core or hexicore processors and 128GB of RAM, can run more than 100 virtual desktop instances. VMware's VMotion and Dynamic Resource Scheduling software shuffle the virtual desktops between the machines to balance the server workload. During off-hours, still-operating virtual desktops can be stacked on one server, allowing the other servers to be powered down.

And since all Saint Vincent's locations are within a confined geographic region, and tied together via gigabit Ethernet point-to-point connections, the network latency is minimal, Hansen said.

In a survey done last year with 2,000 IT managers, Forrester Research found that one-third of them were either deploying are planning to deploy desktop virtualization on thin-client hardware or other terminals. And roughly another third, or 31 percent, were interested in the possibility of such deployments.

Factors such as improved security, easier management and disaster recovery, as well as the improved flexibility of Windows 7 and other OSes all contributed to the warmer reception toward client virtualization, according to Forrester.

"Beginning in 2010 but flourishing over the long term, the 'corporate desktop' will no longer be a physical machine but a virtual image that users will access from whatever device is most convenient at that time in that particular location," a summary of the survey reports.