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Some racks now provide expansion channels that help with cable management and ease
heat removal for high-density racks. It may be possible to retrofit existing racks with these
channels.
Some organizations are also running cabling above or through racks, rather than under
the floors, to reduce the interference with the flow of air from below. Further, some
organizations are deploying advanced power strips to bring the power load closer to the
rack rather than running so many cables through the datacenter. We’ve all seen messes of
cabling that resemble an enormous blue or grey spaghetti bundle. These bundles act like
insulation, trapping heat near the equipment and preventing cool air from passing through.

Vapor Seal
It’s also important to ensure you have a good vapor barrier in your datacenter, cutting it off
from the rest of the building. If you have a poor vapor barrier, humidity will move into the
datacenter during hot months and escape during the winter months.
A good vapor seal reduces the costs to humidify or dehumidify.
Prevent Recirculation of Equipment Exhaust
Your networking gear can get hot enough on its own and doesn’t need help from its
neighbors—nor does it need to heat up its neighbors. The following are some simple steps
you can employ in your datacenter to prevent exhaust from being reabsorbed by other
devices. These are illustrated in Figure 4-6.
1. Hot-aisle/cool aisle Employ the hot-aisle/cool-aisle design mentioned earlier in
this chapter.
2. Rigid enclosures Build rigid enclosures to keep exhaust heat from being sucked
back into the device’s cool air intakes.
3. Flexible strip curtains Use flexible strip curtains to block the open air above your
racks that have been configured into a hot-aisle/cool-aisle layout.

3. 1.
Hot aisle Cool aisle

6.
5.
2.

4.

FIGURE 4-6 You can prevent exhaust from overheating your equipment by following some simple steps.