Rack vs. blade

January 2015

Data centreThe topic of energy efficiency in data centres has been the major talking point among data centre professionals for some years now. There are opposing schools of thought surrounding which servers are the most efficient and which are the most effective. Tim Pat Dufficy, managing director of ServerSpace examines the world of data centres and offers his take on the situation.

In 2012, a study commissioned by Cable & Wireless Worldwide1 asked data centre decision-makers what their thoughts were on the energy efficiency of data centres. To meet the insatiable demand for faster computation, 55 per cent of respondents felt that they would need to increase data centre capacity over the next two years, with 38 per cent saying they’d require physical servers to accommodate this capacity growth.

Whether these physical servers will take the form of a blade or a rack is a decision for the management staff, but overall efficiency remains at the forefront of their minds.

Until 2006/7, server manufacturers were only really listening to their customers in corporate America. The demand for more powerful servers had reached a critical point, but so had the electricity bill. Major vendors were simply responding to this demand and concentrating on faster computation speeds at the expense of energy consumption.

Chief financial officers had to pay huge energy bills for the running of their data centres, so the focus and demand changed for more energy-efficient servers that maintained the computation speed.

This brought about the birth of the blade server, with its more slender appearance and with shared network, power supply and cooling system on the chassis.

The pros and cons of blade servers

Data centre professionals can be mistaken for thinking that there has been an evolution from rack to blade servers. It’s easy to think that a blade server is more advanced due to its more modern exterior and its cost-efficiency, but they have their faults - just as their rack counterpart does. Each option has its benefits, just as they have their drawbacks. However, both essentially approach the energy efficiency problem from different angles.

Blade servers combine the power of many computers and allow companies to develop a server farm in a compact space, where network tasks are distributed among multiple servers. However, because they all share a common power supply, network connection and cooling system, it does bring about problems.

One major disadvantage of a blade server is that the majority are designed to work with a single type of blade, made by the same hardware manufacturer. Mixing blades that are made by different manufacturers can reduce performance.

The heat generated by blade servers can also be a problem in a data centre. Unlike rack-mounted servers, blade servers share a common cooling system so a failure with the cooling system can greatly affect the performance of the servers, whereas rack-mounted servers have their own individual cooling systems, so damage control is far easier to implement.

The cost-effectiveness of a blade server isn’t recognisable until you have a significant number of blade servers within the enclosure. Additionally, if the chassis that the blade servers are contained in stops working, it will affect all of the other blades in the enclosure.

Blade servers also fall down on the fact that they can be quite complicated to configure and require a trained in-house IT department or the paid installation by an IT representative from the manufacturer. The costs of the initial set-up can also be fairly substantial, so businesses may decide to choose an alternative instead.

Due to the cost of blade server installation, it can limit a business as there is no real scope for updating the hardware without completely replacing it. Server speed is advancing at such a rate that if businesses are bound by a blade complex, they could find that the unit is rendered redundant after five years or so.

Although blade servers are arguably more efficient than their rack counterparts, the cost of maintaining them can rise quite considerably. Businesses must ensure that they have highly-trained staff that can operate the servers and use them to their full potential; otherwise the running costs will mount up quickly.

Virtualisation and big data

The research conducted by Cable & Wireless Worldwide suggested some interesting trends in terms of what data centre professionals feel will happen over the next two years. Most respondents thought that both the demand for physical and virtual servers would increase due to the fact that the amount of data consumed is doubling every two years.

‘Big data’ has been the buzzword in the data centre industry. The argument of how to manage big data both efficiently and effectively divides the industry, with many citing virtualisation as the solution for managing big data.

Virtualisation enables an individual server, either rack or blade, to run multiple virtual servers while replicating all the components of a physical server. Since virtualisation is compatible on both rack and blade servers. It essentially comes down to the efficiency of those servers; how much energy they use and what the cost is of cooling them.

The research from Cable & Wireless Worldwide found that 53 per cent of so-called ‘data centre decision makers’ reviewed their energy costs ‘from time to time’ or every 12 months or less. As the research correctly identified, because 70 per cent of data centre operating costs are made up from energy consumption, the fact that over half of those surveyed said they only reviewed costs from time to time is staggering.

Virtualisation, hailed as a solution to ‘server sprawl’, can also be mistaken for an evolution as it still requires rack or blade servers to operate. However there are key benefits to implementing virtualisation.

The main benefit is that virtualisation increases the utilisation of already existing server assets. This in turn results in huge savings in operational costs, as less power is required once the systems are all in place. It can also make back-up functions and system recovery more manageable.

However there are certain drawbacks to virtualisation. Data centre professionals must remember that the virtual environment is shared so it can be more difficult to know what each server is doing at any given time. Therefore if the performance of one server is affected it can have a knock-on effect on the other servers, potentially leading to significant periods of downtime. Also adding virtualisation technology into a solution adds a level of complexity that can lead to difficulties with fault finding and resolving outages.

What is the right fit?

There hasn’t been an evolution between rack and blade servers. It’s arguable whether virtualisation is really an evolution either. Both rack and blade servers are product types that were created to serve the needs of different customers.

Using rack or blade servers both have their advantages as well as their disadvantages. Blade servers cannot be easily upgraded and can end up costing businesses a fair amount of money and they can be expensive to cool as they generate a lot of heat within a confined space.

Rack servers fall down on the fact that they use more power than blade servers, but the blade power supplies must fit the power usage of the blade server system. Rack servers also take up more space than blade servers.

At the end of the day, each business should consider what the right fit is for them. For example, using rack servers if you have limited space would not be efficient, just as having an inadequate cooling system would be a drain on finances if you wanted to integrate blade servers.

Reference
1. The Data Centre Power Efficiency Study 2012: Inefficiency leaves millions on the table. Survey performed by the Customer Experience Foundation.
 

Image: iStock/450765521

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