My colleague Paul Lin and I recently wrote a white paper that discusses some causes of stranded space, power, and cooling capacity in colocation data centers. Stranded space, power, and cooling are symptoms of low average rack power density and lack of proper air management practices. I’ve learned over the years that, too often, these issues can be traced back to requirements tenants place on the colocation provider and the lack of best practices. Examples of requirements include housing equipment in 4-post racks (or sometimes even in baker’s racks) and irregular rack arrangements. Some tenants are allowed to deploy their IT in a “deploy it your way” fashion with little to no design standards. As a result, these deployments do not conform to cold/hot aisle configuration which may prevent the use of containment strategies, all but guaranteeing stranded cooling distribution capacity. This type of environment makes it very difficult for the colocation provider to ensure a tenant does not cause hot spots for themselves or their neighboring tenants, and makes it more difficult for the colocation provider to ensure their SLA.
This is why I’m a big fan of adding power and cooling best practices to acceptable use policies (AUP). No one would argue against an acceptable use policy that prohibits using the network for spam, or other illegal purposes. But unfortunately, many AUPs today are void of language that fosters good air management practices. Back in the day, there were no air management issues because average rack densities were very low. But today, air management is the most effective way to ensure predictable IT supply air temperatures and to avoid hot spots.
Here’s an example of what tenants should look for in an AUP:
Tenants must comply with the following cooling configuration rules when deploying their IT:
- IT racks shall be configured in a hot aisle / cold aisle arrangement.
- All tenant equipment greater than 6 kW/rack shall use containment and / or chimney racks; supplemental cooling components may also be used to increase cooling distribution capacity.
- All tenants shall seal any open sections of racks using blanking panels to prevent cold air leakage.
- Cable cutouts and gaps between racks shall be sealed to prevent cold air leakage.
- Raised floor tiles shall not be left open except during maintenance work.
- Doors to be used in aisle containment systems shall remain closed at all times unless entering or exiting the aisles and the doors must never be propped open.
In addition to a comprehensive AUP that includes rules like those above, I also advise prospective tenants to look for evidence of these best practices as they tour a provider’s data center. Do you see air barriers that deflect hot exhaust air from one cage away from adjacent cages? Do you see blanking panels on most of the IT cabinets? Do you see brush strip on cable opening? Can the data center support a high density rack (i.e. 10kW)? Validating this type of information will give you confidence that your critical IT resources will be supported reliably and efficiently.
For more information on this topic I encourage you to read white paper 173, Power and Cooling Guidelines for Deploying IT in Colocation Data Centers.