Retrofitting Cold-aisle Cocooning Doesn't Mean Massive Disruption

Mark Hirst, product manager for Cannon Technologies’ T4 Data Centre Solutions, is a Data Center design expert with a background in electronic control systems and industrial networks.

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Working around infrastructure that has evolved over time makes retrofitting hot/cold aisle containment a challenge. Multiple data and network cable runs, cooling pipes and mismatched cabinets mean many solutions will not work effectively. This column looks at the options available to those who want containment, but are not sure if their environment can handle it.

What is Hot/Cold Aisle Containment?

Hot/cold aisle containment is an approach that encloses either the input or output side of a row of cabinets in the data center. The goal is to effectively control the air on that side of the cabinet to ensure optimal cooling performance.

With hot aisle containment, the exhaust air from the cabinet is contained and drawn away from the cabinets. Cold aisle containment regulates the air to be injected into the front of the hardware.

In both cases, the ultimate goal is to prevent different temperatures of air from mixing. This means that cooling of the data center is effective and the power requirements to cool can, themselves, be contained and managed.

Challenges

Over time, all environments evolve. The most common changes in a data center tend to be around cabling and pipe work. What was once a controlled and well ordered environment may now be a case of cable runs (power and network), being installed in an ad-hoc way. In a well run data center, it is not unreasonable to assume this would be properly managed but the longer it has been since the last major refit, the more likelihood of unmanaged cable chaos.

The introduction of high-density, heat-generating hardware such as blade systems has seen greater use of water-based cooling. This requires changes to the racks and the addition of water pipes. These make enclosing a rack difficult as many solutions need to have pipework holes cut into them. The other challenge here is that you cannot simply drill a hole and the retrofit will not include disconnection and reconnection of pipes to run them through the holes.

These are not the only challenges. Just as the type of hardware in the cabinets has evolved, so have the cabinets themselves. What started out as a row of uniformly sized and straight racks may now be a mix of different depths, widths and heights. This is common in environments where there are large amounts of storage present as storage arrays are not always based on traditional rack sizes.

Cabinet design can also introduce other issues. If the cabinet has raised feet for leveling, something often seen with water-based solutions, there may be existing backwash of air under the cabinets. There may be gaps in the cabinets either down the sides or where there is missing equipment. These should already be covered by blanking plates. The reality in many data centers, however, is that there will be missing plates which is allowing hot and cold air to mix.

The floor also needs attention. Structurally, there may be a need to make some changes to accommodate the weight of any containment system. This is not just the raised floor but the actual floor on which the data center sits. The evolution of data centers and changes to equipment is rarely checked against floor loads. Before adding more weight through a containment system, it is an opportunity to validate loads

Floor tiles degrade over time. They get broken, replacements may not be the right size or have the right size of hole. No air containment system can be effective if there are areas where leaks can occur.

Prerequisites

It would be naïve to assume that retrofitting hot/cold aisle containment will not require some potential changes to the existing configuration. However, there are very few prerequisites to address:

1. Weights and floors, as mentioned above.
2. Each enclosure should ideally line up height-wise with its counterpart across the aisle. Don't worry about small gaps, we will deal with those later.
3. The height of each pair of enclosures should ideally be the same. However, there are ways around this but within reason. A height difference of a few inches can be managed easily. A difference of two or three feet or more is increasingly common in older environments. Whilst most containment solutions could not cope with this, we have designed our retrofit solution specifically for such “Manhattan Skylines” which are highly prevalent in many older data centers and where a cost effective upgrade path to containment can significantly extend the useful life of the existing racks, data cabling and M&E infrastructure.
4. Normally, each row must line up to present an even face to the aisle that is being contained, in order to create an air tight seal.

The prerequisites may require a little planning inside the data center and in the most extreme case, require a little moving of cabinets to get the best fit. Again it is possible, as we have done with our own retrofit system, to design a solution for situations where it is not reasonable to move cabinets to create an even line to the containment aisle.

What equipment is required?

Once the prerequisites have been met, fitting aisle containment is a mix of installation and good practice cabinet management.

There are four steps to fitting containment.

1. Fix the ceiling eyebrow to the top of the cabinets. Where there are differences in cabinet heights, it will be necessary to fit blanking panels to create a uniform height both sides of the aisle. It may also be necessary to arrange for cables or pipes to be moved if they are too close to the edge of the cabinet.
2. Install the ceiling panels. These sit inside a framework which should be a uniform size. If the ceiling panels do not fit snugly the containment will be seriously compromised.
3. Fit air skirts under the cabinets to prevent any return flow of air. If the cabinets do not butt up against each other, fit skirts to cover the gaps between the cabinets.
4. Attach the doors at both ends of the aisle.

Tidying up

Tidying up the installation is about good data center management. Here the typical steps include:

1. Fit blanking plates wherever there are gaps inside the cabinets.
2. Fit blanking plates to the sides of cabinets where cables run.
3. Replace broken or damaged floor tiles. If the containment is to the cold aisle, rebalance the cooling by changing the floor tiles for those with the right size of vent.
4. If the containment is for the hot aisle, check that the extraction and venting is evenly spread across the length of the aisle to prevent hot air zones being created.
5. Fit monitoring devices such as temperature and humidity sensors to ensure that there are no unexpected challenges caused by the containment.

None of these steps should cause problems for data center facilities managers and will provide an opportunity to validate the benefits from the aisle containment.

It Can Be Done

There is a belief that retrofitting aisle containment to data centers is highly disruptive, requires a lot of time, is expensive, can have limited benefits and may not be suitable. As can be seen, the process to retrofitting is not essentially complex and builds upon good data center best practices for housekeeping and management. Additionally, the time required to do the retrofitting is easily manageable and can be done without any impact on data center operations.

Retrofitting aisle containment is one of the easy wins when it comes to recovering money spent on power by reducing excessive cooling while retaining, for a good few years more, the significant investment in racks, data cabling and M&E.

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