Hot Aisle Containment VS Cold Aisle Containment | What’s Better For A Data Center?

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Data center containment isn’t a fad. Instead, it has gone super mainstream in the past decade in the data center industry, which has ultimately led to the ubiquitous implementation and adoption by many sites across the world. 

In fact, a recent survey by the Uptime Institute revealed that more than 80% of sites on the planet have implemented either hot or cold aisle containment. Although this survey primarily represents large scale facilities, several medium to small facilities too have either implemented or are strongly considering some form of containment. This immensely high adoption rate has left a lot of people wondering – is hot aisle containment or cold aisle containment better for a data center?

The ultimate goal of hot and cold aisle containment is the same: to enhance the data center environment in ways that mitigate operating costs while increasing cooling capacity. However, because every computer room is different, there is no straight answer to which type of system data centers should employ. As a result, it is critical that you grasp the distinctions between the two containment systems.

Intel and T-Systems conducted a third-party empirical investigation in a data center test lab in Germany in 2011. Their findings were presented in the study “Data Center 2020: Hot-Aisle and Cold-Aisle Containment Efficiencies Reveal No Significant Differences.” The title is rather self-explanatory. As a result, we look to elements other than efficiency economics to assess the relative benefits of the two approaches to containment.

It’s essential to keep in mind that the end goal of both hot and cold aisle containment is the same at the end of the day: To improve and enhance IT equipment intake air temperatures and generate a conducive environment where alterations can be made to lessen the operating cost while amplifying the cooling capacity. 

So, returning to the original question: which is superior? Assuming that a computer room is configured in such a way that either option is available, hot aisle containment may be viewed as the better option due to thermal efficiency and ride-through benefits. Nonetheless, since every computer room is different, there is no one-size-fits-all approach. As a result, it is critical to grasp all of the differences between hot aisle containment and cold aisle containment in order to make an informed decision based on your architectural context and corporate strategy.

To clarify, cold aisle containment entails doors at the ends of the cold aisles as well as some kind of walls or ceiling over the cold aisle. Hot aisle containment consists of doors at both ends of the hot aisle as well as a layout of baffles and duct work from the hot aisle to the cooling unit returns. In addition, drop ceiling plenums are frequently utilized to funnel return air back to the cooling units. Both tactics offer advantages as well as disadvantages:

Let’s have a look at them.

Cold Aisle Containment Advantages: 

  • It is easier to install; no other architecture is needed to control exhaust air and return it to the cooling units (drop ceiling, air plenum, etc.).
  • Only doors at the ends and a cap at the top are needed.
  • Less expensive in general.
  • Cold aisle containment is usually easier to install in an existing data center, especially if there are overhead barriers to avoid, like power and network distribution, ducts, and lighting.
  • Allows more surface area for “cold sinks” (either with or without a raised floor) ride through if there’s ever a power failure or in instances when the engine generators are not starting. 

Cold Aisle Containment Disadvantages: 

  • The total data center becomes the hot aisle in cold aisle confinement, and that space might be significantly hot if the theoretical perks of containment are fully exploited, i.e., greater supply temperatures leading to potentially high exhaust temperatures.
  • There may be no area with a suitable temperature profile for equipment that is inconsistent with living in the containment setup for whatever cause. This may imply decreasing the supply temperature and foregoing some of the economic benefits associated with creating a complete environment for some of these non-contained electronics.
  • Cold aisle containment increases the mixing of the return air, which in turn lowers the delta T. 
  • There’s a looming risk that the conditioned air leaking from the raised floors and entry points under the equipment like PDUs enter the exhaust air paths returning to the cooling units. This diminishes the system’s efficiency. 
  • Complete cold aisle containment leads to what the NFPA codes call a “separate volume.” Therefore, there has to be fire suppression in place for the overall data center space, and then either extra fire suppression for the contained cold aisle or the containment has to be linked to the smoke detection system and eliminate itself as an inhibition on a smoke alarm. 

Hot Aisle Containment Advantages:

  • The open space of the room is a cold environment. 
  • The leakages from the raised floor entry points in the bigger area of the room transfer into the cold space. 
  • Comparatively more effective than cold aisle containment. 
  • Hot aisle containment will be more tolerant of network racks and self-contained equipment like storage cabinets that may have to operate outside the containment design, i.e., in the lower temperature region of the computer room.
  • Hot aisle containment in a slab environment can be achieved by simply flooding the data center with a suitable supply air volume and restricting the exhaust air.
  • Thanks to the containment structures usually abutting the ceiling fire where fire suppression is installed, Hot aisle containment does not create distinct volumes but simply creates obstructions that are required to meet the clearance requirements from the sprinkler heads. It is possible that a typical grid fire suppression system might be placed around a hot aisle containment array of barriers and fulfill code in a well-designed facility.

Hot Air Containment Disadvantages:

  • It is necessary to have a contained passage for air to go from the hot aisle to the cooling units. A drop ceiling is frequently utilized as a return air plenum.
  • More pricey in general.
  • Higher temperatures in the hot aisle cause discomfort for workers working on IT equipment. It’s worth noting that certain server producers are creating and delivering front-serviceable servers, which means that the hot aisle, whether contained or not, would be rarely used.

Final Words

The truth is that each and every computer room is unique. Whether it’s hot or cold aisle confinement, each computer room may show conditions that make one technique more appropriate than the other. The best thing to do is examine your site, weigh the benefits and drawbacks of each method, account for bypass airflow, and utilize this knowledge to determine which strategy is best for you and your institution.

TRAX data center containment solutions are currently being used by some of the most recognized names in the high tech world.
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