Containment – Is it worth the investment?
As we gear up for our webinar, “Containment: Improve DC thermal conditions and maximize IT capacity,“ we’re taking a closer look at why you should consider deploying containment in your data center. What containment solution is best, how much will it cost, and what kind of payback can you expect?
What do you really get out of it?
As more reliance is placed on data centers for the operations that influence and even control many aspects of our lives, the need to provide adequate cooling for the IT equipment has increased exponentially. As the processing power of IT equipment increases so does the power draw and heat generated by servers.
Containment, done properly, enables more IT equipment to be added and increases the energy efficiency and effectiveness of cooling systems avoiding the need for the deployment of more cooling systems.
Why should you consider adding containment to your data center space?
Air is the most common means of cooling IT equipment, but it does have many limitations. First, air does not absorb heat as well as a liquid and so more attention must be paid to ensuring air being delivered to cool IT equipment is within the proper temperature range. Secondly, air temperature is easily influenced and can rise dramatically just by passing through a heat source. Air is invisible; you can’t tell where it’s going. Cooling air does require a great deal of energy and if the cooled air is not delivered to the inlets of the IT equipment at the proper temperature, a large portion of the energy cost has been wasted.
Mixing of cool supply air and warm exhaust is an issue every data center encounters, which reduces the effectiveness of the cooling approach. Separating the cool supply air from the warm or hot exhaust air is a significant step in improving cooling energy efficiency and effectiveness. But there are lots of other reasons that air containment should be considered.
What is containment?
Containment can take many forms but the basic principle is the same – separate the pathways of the cool supply air from the pathways of the warm or hot exhaust air in the data center.
It all depends on your space
Containment can be as simple as adding blanking panels to the empty spaces in racks or filling the voids between racks with panels to prevent air mixing. It can be as complex as hot or cold aisle containment with sensors to feed data back to the cooling system to control their operation. It can consist of chimneys on the exhaust side of racks to capture the warm exhaust air and move it into the ceiling return plenum. These chimneys can be passive allowing free flow of the warm air or active with fans to push the warm air upwards.
Containment can be rigid, with solid panels and doors, or soft with the use of curtains to enclose the desired space.
Hot Aisle or Cold Aisle?
Hot aisle containment captures the warm exhaust air, moves it into the ceiling plenum allowing the warm air to return to the cooling units without losing heat. In these types of installations, the remainder of the data center becomes a large cold aisle.
Cold aisle containment encloses the airflow from the perforated tiles using doors at the end of the cold aisles and a roof over the cold aisle. This forces the cool air to move through the IT equipment before entering the larger room space. Depending on the size of the space and the kW load of the racks the area outside the cold aisles may become noticeably warmer.
Another form of containment is the use of rear door heat exchangers (RDx). In these installations, the rack is equipped to cool the exhaust air prior to it being exhausted into the room. The RDx can be passive, allowing the air to flow through the cooling coils on the doors or active, with fans on the rack rear door to push the cooling air into the room.
How do you know if you need containment?
Typically, the need for containment is driven by the kW rack loads. Once rack IT loads start moving into the 5-6 kW range containment should be considered. Standard perforated tiles, 25% openings, can support IT loads of 4-5kw but as racks begin to exceed this level, supplying sufficient airflow to meet cooling needs is challenging.
There are always lots of “what if’s” when considering containment.
What if there are only a few racks, say 5% of all racks, that are exceeding the 5 kW level? What if only one area of the data center has racks of higher kW loads? What if the higher density racks are scattered throughout the data center?
In a legacy data center, there is no single answer. Containment solutions could consist of adding chimneys to a few racks or only adding containment to racks in one area.
The best way to determine what is needed is to have a reputable company assess the data center and provide expert advice. In some cases, doing airflow modeling will help to provide direction on the best solution.
What type of containment is best for my data center?
There is no “one size fits all” containment solution. In a lot of cases, the geometry of the room will determine what type of containment can be added. Cold aisle containment can be more adaptable for legacy sites. For example, in an existing data center with no dropped ceiling cold aisle containment may be the better solution as hot aisle containment would require the addition of a ceiling. Rigid containment with end of aisle doors and roof does a great job of containing the cool supply air but the enclosed space can encounter higher pressure which reduces the airflow through the perforated tiles and in turn reduces the cooling effectiveness.
If the cooling system delivers air via overhead ductwork, end of cold aisle doors or curtains may be the most feasible. If the rows are in classroom style layout containment may not be a good alternative at all.
New builds quite often lean toward hot aisle containment. This is appealing as it directs the heat back to the cooling units quite efficiently and the white space outside the containment areas remains at a comfortable temperature. One concern though is hot aisle containment can make working conditions in the hot aisle quite uncomfortable as temperatures may be in the 32 to 38°C range (90 to 100°F). In a legacy data center, a dropped ceiling addition will be required to act as a return air plenum. Cooling units will need to be chimneyed into the ceiling plenum space to pull the warm air back to the units. If the cooling units are upflow units with cool air being ducted to the rack rows hot aisle containment is likely not a viable option.
Rack chimneys are a good option provided the racks are of sufficient depth to allow the exhaust air to move away from the IT equipment. In some cases, the airflow can be assisted by fans which of course raises the question of a power source for the fans. In an enterprise data center that may not be an issue but in a colo data center where the customer charges are based on kW this may be a concern. Also adding fans to chimneys creates another point of failure which, if fan failure does occur, could cause the IT equipment to overheat and fail.
It’s important to note studies on the difference in energy efficiency of hot or cold aisle containment have concluded there really is no difference – both offer similar improvements in energy efficiency.
What does containment cost?
Containment can take many forms, and therefore material costs and installation will vary widely. Before committing to any form of containment it’s important to make sure you’ve accurately assessed your space to guarantee the best solution for your data center. If you are considering adding containment, you should answer these questions:
- What are the current rack kW loads?
- Will kW loads continue to increase over the next few years?
- Is there a virtualization program that may significantly reduce the number of servers and racks in the data center?
- Will the virtualized servers be concentrated in one area, thereby changing the heat density profile of the data center?
- Will there be racks added to the existing rows or will existing racks be swapped out for racks of different sizes or racks eliminated altogether?
- How will you handle concerns of working conditions in contained hot aisles?
- How will containment impact existing fire detection and/or suppression systems?
These questions are only a few that should be addressed and understood in order to develop a containment strategy.
How important are these considerations?
We’ve seen a number of data centers where the skeletons of failed containment installation remain after the removal of containment. These installations failed because the conditions of the data center were not fully understood. Aspects such as airflow patterns of the room (airflow modeling would help) were not understood, or the wrong type of containment (hot aisle rather than cold aisle or vice versa) were installed. Or the containment was not designed to accommodate changes in racks.
What is the payback of doing containment?
The most straightforward payback is that IT equipment can operate in a more controlled environment. Installation of the proper type of containment will ensure the IT equipment is getting inlet air at the right temperature. Variations in air inlet temperature throughout the white space should be virtually eliminated.
By separating the cool and warm air the return air to the cooling units will be warmer meaning they will operate more efficiently. The air separation also means less supply air will be required to meet the needs of the IT equipment.
Temperature set points can be moved up on the cooling units, another step to making them more energy efficient. Humidity levels will also be more consistent throughout the space as well.
By increasing the efficiency of the cooling units and reducing the amount of cooling needed added capacity to accommodate more IT equipment will result. This can amount to a capacity increase of 50% or more.
In a colo data center that means more client IT equipment can be added without having to buy new cooling systems. In an enterprise data center cooling costs will go down and the need to expand the data center or add more cooling units can be deferred.
How do you find out more?
On January 27th we’re teaming up with our containment partner, Polargy Inc, to discuss containment alternatives and strategies that can be applied to your data center. Case studies will guide our discussion around how to determine the appropriate containment solution for your data center and achieve measurable results. Understand the OPEX and CAPEX benefits associated with containment as we demonstrate solutions that will reduce cooling energy costs, eliminate hot spots, and expand the capacity of your data center.
Register today to join us for “Containment: Improve DC thermal conditions and maximize IT capacity.”