CONTAINMENT – IS IT WORTH THE INVESTMENT?
Containment, done properly improves the data center thermal conditions, enables more IT equipment to be added and increases the energy efficiency and effectiveness of cooling systems avoiding the capital cost for the deployment of more cooling systems.
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 above 6-7 kW per rack containment should be considered.
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 this 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? These questions should be addressed before moving ahead with any form of containment.
WHAT TYPE OF CONTAINMENT IS BEST FOR MY DATA CENTER?
For existing data centers there is no “one size fits all” containment solution. In many cases, the site architecture will dictate what type of containment can be added. Cold aisle containment may be more adaptable in an existing data center with a raised floor and no dropped ceiling. Rigid containment with end of aisle doors and roof does a great job of containing the cool supply air but the enclosed space may encounter higher pressure which can restrict the airflow through the perforated tiles and in turn reduces the cooling effectiveness.
If the cooling is 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 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 uncomfortable as temperatures may be in the 32 to 38°C range (90 to 100°F).
Rear door heat exchangers (RDx) are a containment alternative for sites with a few high-density racks. In these installations, the rack is equipped to cool the exhaust air prior to it being expelled 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.
Rack chimneys were once considered a good alternative, however due to poor air flow and cabling congestion they are now considered a less attractive alternative.
WHAT DOES CONTAINMENT COST?
Before committing to any form of containment it’s important to make sure your space is properly assessed to guarantee the best solution.
If you are considering adding containment, these questions need to be answered:- 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 are only a few that should be addressed and understood in order to develop a containment strategy.
HOW IMPORTANT ARE THESE CONSIDERATIONS?
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.
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 – therefore cooling units will operate less.
Temperature set points can be increased 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, more capacity to accommodate IT equipment will result. This can result in 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.
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.
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 FIND OUT MORE?
Containment is an enabler to increase IT capacity. The experts at SCTi are here to assist you to evaluate the best containment solution for your infrastructure.