Running the blade? Plan ahead
There is no doubt that blade servers offer tremendous benefits to the data centre; providing high-density computing that in turn allows for a smaller footprint without the resultant power compromise.
However, whilst blade servers take up less space and allow for the deployment of state-of-the-art technologies like VMware they do require some serious facilities planning and architecture development to gain the most from it.
The upside is that blade servers allow companies to consolidate their operations and employ advanced management tools such as virtualisation.
However, the flip side sees blades wreaking potential havoc on data centres’ power and cooling resources, also known as notorious energy drainers.
A single blade chassis uses up eight kilowatts of power which is more than triple that of a standalone server. Furthermore, it is estimated it can require more than 20-times the cooling of its bigger counterparts, which translates into a mind blowing 120cfm of cool air per KW of power rating.
In a TechTarget 2007 Server Decisions Survey, nearly 30 percent of respondents said that cooling issues were enough of a concern to prevent their organisation from investing in blade servers.
The reality is your data centre might soon resemble a hot kitchen if the heat is not contained. If not the results can become a nightmare, resulting in overheating technology and, worst case scenario, the centre shutting down altogether.
So what can the IT department do to mitigate the potential hazards that come with deploying blades? For one, prudent planning is key. Before upgrading to blade servers ensure that you thoroughly investigate your power and cooling resources – do you have enough capacity to absorb both?
Although using Blade servers allows you to fit more computing power into a data rack one must keep in mind that a single fully populated blade chassis can weigh well over 200kgs each. You then need to be sure that the data racks that are being used can carry this load especially when you plan to
install more than 1 blade chassis per data rack. The APC Netshelter range of data racks are designed to hold way over 900kgs which makes them ideal for this application.
Also, it is not only top air cooling that can becomes a problem, bearing in mind that a single blade chassis consumes up to eight kilowatts of power which in turn requires 8KW of cooling and the average tile vent only produces enough air to allow for four kilowatts of cooling rack.. The
traditional down blower type air conditioners commonly used in data centres are simply not strong enough to handle the cooling demand of blades. APC have addressed this problem with their range of in-row coolers which one installs within the rows of data racks. These not only supply cool air
directly to the areas of demand but also, using temperature sensors dynamically vary the cooling output of the air cooler making this a highly efficient system.
IT departments need to pre-empt problems by implementing data centre planning software that will provide them with insight into the centre “hot spots” allowing for the optimum physical implementation of blades.
The way that most IT equipment is designed to handle air flow is to suck cool air through the front panel of the equipment and expel it through the back so if you have a data centre with more than one row of racks, you need to make sure that the front doors of the racks do not face the back doors of
the row in front of it as the servers housed in this rack will suck up the hot air produced by the computer equipment in the front row of racks. This could result in the equipment in the back row overheating. To avoid this, you need to create a hot aisle cold aisle environment within the data centre where the front doors and the back doors of the various rows of racks face
each other. You must also be sure not to allow cold air into the hot aisle as this will result in the computer room air conditioner (CRAC) working inefficiently. The hotter the air which is fed back to the CRAC the more efficiently it will work. The use of blanking panels has also largely been
underestimated, regarded by some as purely aesthetic. The truth of the matter is that these seemingly simple rack accessories are a vital part of efficient cooling of IT equipment within the data rack. Open spaces between servers and other pieces of equipment will cause the cool air in front of
the rack and the hot air behind to mix causing the housed equipment to be hotter as well as inefficiencies in the cooling of the data centre. If one deploys blade servers in this environment, the result could be a catastrophic failure.
The reality is if you don’t plan ahead you might incur unforeseen costs down the road; power and cooling demand alone can double your budget, making the initial cost savings negligible.
This said, while a lot IT departments point out the costs and other issues inherent with blade servers; they are also adamant about never going back to standalone servers. The ease-of-manageability, virtualisation and computing power are major plusses.
The key is not to be caught off guard. Ensure that you manage and monitor your data centre continuously. Also, do your homework and invest in brands that that have made strides in curbing cooling and power drainage – such as Dell. Dell has as added intelligence the Chassis Management controller (CMC) of its blades such as the Dell M1000E blade chassis which allows for
the the dynamic distribution of power and cooling within the blade chassis itself According to Dell this cutting edge innovation results in 25 % more performance using less power and cooling compared to its nearest competitors.
Ultimately, in order the harness the power that comes with blade servers, you need to plan, plan and plan again.
Robert Brandt
Drive Control Corporation
robertb@drivecon.net
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