Blade IT systems

There are currently two very different IT applications that use the term blade – blade servers and blade PCs. The term ‘blade’, itself, is largely generic and is presumed to derive from the slight depth of the piece of equipment and its suitability for being stacked in a compact, modular system of racks, allowing each blade to be interchangeable and used on a plug-and- play basis.

Blade PCs

Blade PCs arrived on the market in 2001. These allow companies to take computers off users’ desks, and effectively centralise them in a secure location, where they take up minimal space. The functions of the end-user PC, which is effectively a standalone computer (ie processor, memory, hard drive, graphics and operating system) are all embodied in the blade. The blade then sits in a rack similar to a blade server. A small desktop device connects the desk- mounted monitor, keyboard, mouse, USB devices and other equipment with the blade – and the blade, in turn, communicates directly with the company network.

The main problem with the development of these systems to date has been the physical distance between the desktop peripherals and the blade. There are currently only two or three blade PC systems available; however the market is very much in its infancy, and several other manufacturers are developing these systems.

Demand is expected to rise steadily for blade PCs over the next few years, and it is predicted that they will account for 2-3% of the desktop PC market by 2009.

Applications

Blade PC systems can potentially deliver substantial benefits to users who require reliable and secure information systems, operate in a large, highly centralised, high density environment and do not require portable PCs. Dealer floors in financial institutions are perhaps the best example, where some users have as many as four PCs on a desk.

Advantages

• Manageability – support costs are reduced as there is no floor equipment to deal with. Also, if a PC goes down, then rather than having to take it off-line and summon support staff into the workspace to deal with the problem, the user can be switched remotely to a spare blade with the same functions in a matter of seconds and carry on working seamlessly. The result is a higher uptime for staff.
• Security – in effectively moving the PC into a central, secure location, the risk of theft and damage all but disappears. Also, the users’ ability to download or upload software or data can be strictly controlled, which can be a significant benefit.
• Environment – in taking PCs off the floor, valuable space is made available, fan noise is eliminated and, since the heat load across the floor is reduced, the costs of cooling the space will also come down.
• Increased utilisation – through the appropriate software, it is possible to utilise blades for other purposes in addition to that of desktop PCs. When blades are not being used during normal working hours, for instance, they can be assigned other routine non-PC based processing work remotely.
• Space saving – a 42U rack (a U is defined as a standard unit 1.75 inches high) can hold 112 blades, covering an area of approximately 0.5m2. Compare this with the equivalent area that 112 PCs would take up when distributed over an office or trading floor, and the benefits in this respect are clear.

Cost benefits

The increased capital costs associated with PC blades, compared with a conventional desktop PC solution, can be recouped through reduced hard and soft operating costs. Analyses of companies that have adopted blade PCs show a payback of between one and two years, through savings in the following areas.

• The removal of desktop PCs from the workplace reduces facilities costs in terms of space, HVAC and electricity.
• Less wear and tear to PCs, and therefore reduced maintenance costs.
• Risk of PC theft is virtually eliminated.
• Potential reduction in hardware costs, as blades can be utilised for longer periods and are not subject to office hours in a single location, as would be the case with desktop PCs.
• Reduction in IT support staff and greater productivity of remaining IT staff as PC centralisation allows them to work more efficiently.
• Increase in user productivity and, crucially, a significant reduction in downtime. As operation can be easily switched to a spare blade, there are fewer problems for the user to deal with and a corresponding reduction in help desk calls etc.

Blade servers

Blade servers in data centres sound extremely futuristic, but in reality these are essentially a set of compact motherboards with a common power supply and a common means of cooling.

Advances in technology mean that significantly more processing power can be concentrated in increasingly smaller units, and blade servers are the current manifestation of such technology in the marketplace. Blade servers carry out exactly the same function as conventional servers, but are smaller, faster and higher in capacity, and represent the leading edge of modular hardware.

Blade server technology is becoming an increasingly important element of data centre infrastructure and is expected to feature prominently in the next generation of centres. The technology allows them to be flexible in responding to changing business conditions and be more cost effective.

The current crop of blade servers are suitable replacements for both rack-mounted and standalone servers in a variety of tasks. The first versions, which came on the market over three years ago, were intended to consolidate the sprawling racks of small servers that were commonplace at that time. However, the industry has since matured and several product streams are now available, differentiated by their degree of connectivity (in terms of power distribution and supply, cable consolidation etc), integrated management capability and processor performance and density.

Advantages

• Flexibility – standardised components designed on a highly modular basis allow for rapid scaling up and down and rapid replacement of components.
• Manageability – allowing for immediate re-configuration and swapping of servers, thus minimising downtime.
• Reduced data centre costs – provided by the potential to pack more processing power into a given space. However, the increase in power consumption and heat output means this is unable to be fully realised until reduced power processors become available. Manufacturers are currently developing ‘low utilisation’ server technology in order to reduce power consumption by reducing the processor speed, since the key to realising the true benefits of compaction provided by these servers is to reduce the corresponding power requirement.
• Potentially more efficient infrastructure, reducing the total electricity consumed.

Disadvantages

• Failure management – where the rack has a single power supply, its failure could potentially take out the whole rack of servers. Some users have opted for individual devices, providing more security.
• Replacement costs – a single blade can cost significantly more than a non-blade server. In high density deployments, the latter is relatively inexpensive.
• Although there is a space saving advantage in using blades, the corresponding increase in power consumed and heat generated means that there may not be an overall decrease in costs for the user – particularly where the data centre is not run by the user, but by a host provider, with direct charges for power and cooling.

Cooling for blade servers

The single greatest issue in the contemporary data centre is maintaining adequate cooling and air movement given the intense heat gain of modern blade server and direct access storage device equipment.

The graph on page 53 shows the increasing heat load densities that cooling systems are having to deal with in data centres.

Traditionally, computer room environments have been controlled by a series of computer room air conditioning (CRAC) units positioned around the perimeter, pushing out cooled air at high air change rates. These units have an upper limit of 1-1.5 kW/m2. With the power draw of a typical cabinet being 3-4.5 kW, one cabinet requires a floor area of around 3 m2.

The increased power densities of blade servers mean that a typical cabinet could have a power consumption of 20–30 kW, which is beyond the capability of conventional CRAC units.

Alternative approaches

• Separating the high-density server racks across the entire floor and reducing hotspots – this provides a more even cooling load.
• Conversely, group together high density racks and treat them separately from the remainder of the equipment.
• Spread the high-density loads between racks – although this is not ideal as it increases the number of racks and corresponding space requirements and means that some racks are left partly empty.
• Use airflow assisting devices attached to floor grilles or within racks to direct cool air over the heat-producing equipment. These can increase cooling capacity to 3-8 kW per rack.
• Provide direct cooling to racks via chilled water, either standalone or in conjunction with CRAC units – cooling via water is considerably more efficient than air and several manufacturers have developed this type of product specifically for this market. Taking the heat away at source is highly effective and allows for higher density loads –in excess of 8 kW per rack– to be achieved.
• The use of carbon dioxide cooling systems which can handle cabinet loads of up to 30 kW – see BSj 08/05.

Cost analysis

The cost analysis in the table above is intended to provide indicative costs only for providing blade PCs to a 2000 m2 dealer floor, compared to a conventional desktop PC system.

The conventional desktop PC system is based on a total of 400 desks, each with two PCs and four monitors, with the floor being air conditioned via a VAV system.

The blade PC solution is based on four monitors running off one blade which, while perfectly feasible, does depend on the applications required from each machine. With this solution, the floor is air conditioned via a fan coil system.

While there is a premium to be paid at the outset in the use of blade PCs – in this case £177,000 – the savings in the reduction in IT support alone on a dealers floor, where user downtime is critical, would mean this is likely to be recouped within two years.

However, in a business environment where profitability is measured in minutes and is totally dependent on PCs, the advantages of blade PCs are clear and the initial cost premium could be seen as a small price to pay.