Engineering
Datacenter Designers and Engineers Can Solve Cost, Energy and Environmental Challenges by Thinking Inside the Box
High-density blade servers, the processing heart of the broadband internet, are radically challenging datacenter design thinking. The outside-in thinking,
where a load of heating would be designed to match with a cooling load at the room level, is proving costly and inefficient.
In the July 18, 2007 issue of The Data Center Journal, author Lisa Raffin documents:
“Adequately housing and cooling the new servers—and dealing with the resulting increase in energy costs and operational budgets—are a pressing issue for
datacenters, many of which lack the infrastructure to address these issues today. In fact, according to Gartner, 50 percent of all datacenters will lack
sufficient power and cooling capacity to meet the demands of the new high-density computer equipment by 2008.”
Datacenters today need to be designed to integrate the computer cabinet into the overall cooling design scheme.
The cabinet must be designed to act as an integral part of the air distribution system.
All airflow required by the cabinet must be capable of being metered to conserve cooling capacity, fan energy at the computer room air conditioners (CRAC/CRAH)
and static pressure in the floor void. Cabinet induction fans must be used to break up short-cycling air patterns within the cabinet and allow cooling capacity
from the raised floor to be mixed with room air.
The room cooling approach has many well-documented shortfalls. Jack Dale Associates documented the following problems with the approach based on an analysis
of more than 3 million square feet of datacenter space.
- Managing static pressure was poor; studies show that the static was less than 0.025 in the water column (WC).
- 20-ton central room air conditioners (CRACs) were running between 11 and 15 tons.
- Datacenters running at 62 to 68 degrees are short-cycling CRACs.
- Raised-floor cooling from more than one CRAC is not one big mass of pressurized air, but, in fact, a series of individual under-floor air plumes.
- Redundancy and primary cooling capacity is wasted and becomes unavailable for support to overheating areas of the floor.
- Cabinets are running at temperatures that are between 20 and 80 percent higher than the room temperature.
- Excessive openings in the raised floor cause plumes to shrink, covering less floor area.
- Lack of integration between HVAC and cabinet designs straps datacenter managers’ options to control datacenter cooling dynamics that cause hot spots.
- Most of the time, perforated tiles in raised floors help mitigate proper cool air management and adds to the inefficiency of existing cooling systems.
- Convection cabinets can only handle up to approximately 800 watts of power. Fans in mesh-fitted convection cabinets show little improvement due to short cycling.
Datacenters designs today need to overcome the issues. Ensuring full efficiency throughout the cooling flow means looking at all parts of this dynamic exchange as an integrated system. Old assumptions can lead to many of the problems listed above.
For more details on systems to meet the needs of the new high-density generation of servers, click here.
