He who lives by the blade...

Dandy Blade servers are carving a niche in cramped data centers, thanks to their compact form and advanced performance. But they bring new dangers in their high demand for power, cooling and floor support.

Bill Clifford, CEO of Aperture Technologies, says that if you're going to wield the blade, you need to plan your defense.

Those that live by the blade, often die by the blade. While high density equipment enables data center managers to fully exploit their racks, it dramatically increases the risk of a power outage.

According to Data Center Journal, blade servers can demand up to 25 times the power of a conventional server, and most data centers today were built before anyone had dreamed of that kind of power consumption - let alone planned for it. In many data centers, a few blade servers in the wrong place could easily overload the physical infrastructure.

Blade servers are selling faster than ever, with Gartner reporting a 33.5 per cent increase in shipped units in 2006. That's against industry wide growth of only 9 per cent, suggesting that more and more data centers are turning to blades.

The Aperture Research Institute surveyed 100 data center professionals representing over 500 data centers worldwide and found that 27 per cent will buy blades for over 20 per cent of their new server deployments, and a further 27 per cent will buy blades for between 6 per cent and 20 per cent of their new servers.

It's easy to see why blade servers are popular at a time when many data centers are running out of rack space. With their compactness and shared features, blade servers appear to maximize the use of space while simplifying management.

The shared infrastructure of the blade server chassis offer additional efficiencies by bringing together power, cooling, network access and management.

But compact equipment is a double-edged sword. While it increases the server capacity of a rack, the compactness of blade servers also increases power density and so requires careful planning for energy input.

There's also the cooling to consider: Conventional wisdom holds that 100 watts of power consumed by IT equipment will require an additional 60 watts of power to cool that equipment. One simple solution to the cooling problem has been for data center managers to leave spaces in blade racks for air circulation and convective cooling.

But that directly contradicts the purpose of the blade server: there’s no point in having compact equipment if it needs a halo of fresh air around it. In that case, there’s a big difference between the size of the case and the space blades demand in the data center.

One reason that managers leave empty spaces around blade servers is that they don't have sufficient insight into the hot and cool areas of their data center, or the equipment around them.

To make the most of blade servers, data center managers need to be able to plan and manage their deployment. For optimal cooling, the highest density servers should be located in the coolest parts of the data center, and racks should be configured so that air intakes face cool areas and avoid exhausted hot air from other blade servers.

As well as the greater demand for power and cooling, blade servers can exert a much greater weight on the data center floor. A rack full of server equipment that may have weighed 300lbs with older technology, may weigh up to 4000lbs if full of blade servers. That kind of weight needs to be carefully planned.

Given the enormous pressure blade servers exert on the power, cooling and physical infrastructure, it is essential that managers have a clear insight into the use and availability of all key resources across the data center. That needs to be available in real time, using clear visual reports, so that everybody can understand.

Blade servers might help data centers to avoid reaching full capacity in terms of rack space, but they move it much closer to full capacity in terms of power, cooling and weight.

As a result, the margin for error is reduced. Aperture Research Institute found that over 57 per cent of data centers have experienced an outage caused by human error. There needs to be a clear process for provisioning blade servers, supported by reliable information about current data center use.

The secret to wielding the blade is simple: if you fail to plan, you plan to fail.

19 April 2007