There’s no doubt that data center containment has gone uber mainstream in the last decade or so – resulting in a widespread implementation and adoption across all industry vertices. Hence, there’s absolutely no doubt that data center setups are here to stay – they aren’t another technological fad.
However, data centers today are facing a multitude of cooling challenges in the face of rapidly accelerating energy consumption rates and mounting energy costs. One of the most difficult challenges data centers face is ensuring the cooling systems can keep up with the ever-demanding technological challenges, upgrades, and client needs.
In this blog edition, we will share in-depth information on the critical considerations you have to make when implementing data centers.
Choosing Between Hot Aisle And Cold Aisle Containment
According to a recent survey by Uptime Institute, over 80% of sites have adopted either hot or cold aisle containment. Although the survey revolved mostly around more extensive facilities, we sure know that several small to medium facilities have either implemented or are considering some form of containment.
However, when it comes to choosing between containment strategies, the most widespread confusion is mostly regarding whether to opt for hot aisle containment or cold aisle. Keep in mind that irrespective of what you choose, the end goal is the same – separating the flow path of conditioned air from exhaust – which in turn helps in minimizing the operation costs, reducing PUE, and enhancing cooling capacity.
All cases and all needs are unique. However, suppose that a computer room has been configured in such a style that either containment style is feasible. In such cases, hot aisle containment is often deemed to be the superior option as it has some working environment and ride-through advantages.
But as it goes without saying, all computer rooms are distinct, and their needs are even more tailored. So, there’s no “one size fits all” rule here. And for this very reason, it is imperative to fully understand the differences between hot and cold aisle containment in order to make the right decision that best fits your business strategy and architectural environment.
In short, cold aisle containment includes doors on the ends of the cold aisles and, to some extent, of partitions, baffles, or roofs over the cold aisle.
On the other hand, hot aisle containment involves doors on the ends of the hot aisle and a configuration of ductwork or baffles from the hot aisle to the returns of the cooling units.
Most often, drop ceiling plenums are used as the means to duct the return air back to the cooling units.
Both hot and cold air containment strategies have their fair share of benefits and challenges. Let’s have a quick look at them:
Benefits Of Hot Aisle Containment
- The open and bigger area of the room is the cold environment.
- The leakages from raised floor openings in the bigger area of the room transfer into the cold space.
- Allows more surface area for cold sinks with or without a raised floor for a ride through in case of engine or power failure.
- Comparatively easier to implement to maximum efficiency
- Hot aisle containment can function well in a slab environment by simply flooding the data center with ample supply air and containing the exhaust air.
- Hot aisle containment is far more forgiving for stand-alone equipment like storage cabinets, as well as network racks, which might have to be kept outside the containment architecture, i.e., they will live in the computer room’s low-temperature area.
- Hot aisle containment, thanks to the containment structure that typically abuts the ceiling where the fire suppression is installed, is not creating distinct volumes but simply forming obstructions that need to meet clearance needs from the sprinkler heads.
- Given the well-designed space, it is highly conceivable that a standard grid fire suppression system can be installed around hot aisle containment.
Disadvantages Of Hot Aisle Containment
- Comparatively more expensive than cold aisle containment
- Needs a distinct, contained path for the air to pass from the hot aisle to all the way to cooling units. In most cases, the drop ceiling is used as a return air plenum.
- The hot temperatures in the hot aisle can make technicians working on IT gears uncomfortable. However, note that a handful of server manufacturers are now successfully creating and supplying front-serviceable servers. And it means that a hot aisle, whether contained or not, would seldom ever need to be entered.
Benefits Of Cold Aisle Containment
- Cold aisle contaminants are far more easy to install as they do not require the extra architecture to contain exhaust air and return it back to the cooling units like air plenum and drop ceiling.
- A more economical option compared to hot aisle containment.
- Only needs doors at the aisle’s ends or roof or baffles over the aisle.
- Cold aisle contaminants are usually easier to retrofit in an existing data center – precisely when there are overhead obstructions to circumnavigate, like network and power distribution, lighting, and ducts.
- Cold aisle containment doesn’t necessarily have to be on a raised floor – however, it’s primarily because of the challenges associated with transporting supply air to the contained spaces.
Disadvantages Of Cold Aisle Containment
- Leakages from the raised floor plenum that are not contained a cold aisle (such as from under PDUs) will undoubtedly enter the hot area and assimilate with return air, hence lowering the return air temperature. This diminishes the system’s efficiency,
- The full cold aisle containment produces what the NFPA codes call a separate volume. Thus, there should be fire suppression for the overall data center space, and then either additional fire suppression for contained cold aisle or containment has to be linked to the smoke detection system and eliminate itself as an obstruction on the smoke alarm.
- In a cold aisle containment system, the overall data center will become the hot aisle – which means all the areas that are not in the cold aisle will be hot. That being said, if the cold aisle containment is done well – the rest of the space will become dramatically hot if the theoretical benefits of the containment are fully pursued – that means higher supply temperatures and reduction of bypass airflow resulting in high return air temperatures.
- There’s a good chance that there may not be any space with a suitable temperature profile for equipment, which for whatever reason, is not in compliance with the cold aisle arrangement. Thus, this could mean lowering the supply temperature or/and allowing more bypass airflow to accommodate the equipment which does not fit in the cold aisle. As a result, this would lead to losing some critical economic benefits of complete separation.
Maximizing The Benefits Of Data Centre Containment
Irrespective of the strategy you choose to contain the hot or the cold aisle, the airflow containment solutions are the best practices for managing IT intake temperatures with utmost efficiency. But, even after the containment strategies have been applied, sites often fail to achieve the full advantage of the efficiency and cost-saving improvements that containments can provide.
The first step to maximizing the containment is understanding the best utilization of the computer room’s cooling infrastructure. You can do that quite easily by calculating the computer room’s Cooling Capacity Factor (CCF).
CCF is the total rated cooling capacity of operating the cooling units to the estimated heat load. When equipped with this knowledge, you can easily make informed decisions about repairing the maximum benefits of containment solutions in your facility.
Additionally, it’s also critical to consider the overall effects of the containment on the bypass airflow. Bypass airflow occurs when the air’s total flow rate through all the cooling units surpasses the flow rate of the air via IT equipment.
The implementation of containment alone cannot diminish the volumetric flow rate of bypass airflow in the computer room. Conversely, if implemented well, containment will create an environment where the cooling unit fan speeds can be limited, or cooling units turned off to determine the bypass airflow rates.
These adjustments are imperative to fully realize the advantages of reducing fan energy and increasing return temperatures, which in turn enhances the sensible cooling capacity of cooling units.
Hard Versus Soft Containment
Doors, baffles, barriers, and other stiff components are examples of hard containment, whereas aisle-end or over-cabinet curtains are examples of soft containment. Hard containment is preferred over soft containment for a variety of reasons, including aesthetics and effectiveness.
Full Versus Partial Containment
Full containment entirely encloses an aisle’s open space, whereas partial containment seeks to build a sufficient barrier, or a separation between hot and cold air flows, to allow cooling optimum without causing the fire suppression issues that full containment entails.
Evaluate Your Rack Profile And Orientation
The present rack profile, symmetry, and orientation will all play a significant role in the implementation of your confinement approach. For example, if your data center is heterogeneous, with racks of variable heights, widths, and depths, you’ll need to create a highly specialized aisle containment system.
Don’t Forget Peripheral Containment Costs.
Aside from the cost of the actual aisle containment, you will be accountable for a few other expenses, such as:
- Fire safety precautions
- The costs of putting in place a real-time data collection system.
- Implementing centralized CRAC unit controls in existing data centers
- The price of closing raised floor holes and putting up blanking panel walls. These will be used in conjunction with aisle walls to allow better cooling efficiency
Matter of fact – each and every computer room is different. So, whether you’re choosing hot or cold aisle containment, partial or full containment, or hard or soft containment, your computer room will definitely reveal conditions that will make one strategy better suited than the other,
Thus, the best thing to do is to evaluate your site first and calculate the CCF of the computer room.
When you understand each computer room’s particular layout and architecture, you’ll be able to identify conditions that make specific containment alternatives preferable (full or partial, hard or soft). Then, you will be able to select the appropriate containment option for your computer room using this information. Once containment is in place, keep bypass airflow in mind as you optimize for optimal efficiency and cooling capacity.