Proper ToR switch management is all about airflow

Proper ToR switch management is all about airflow

Rack with air movement facilitator unit.

On the surface, everything about deploying top-of-rack switches seems counter-intuitive:

  • Does it really make sense to have more equipment when you could have less in an end-of-row (EoR) setup?  
  • Won't ToR switches increase cooling requirements?
  • Why manage more equipment when you can manage less?

All valid questions. But there are few hard-and-fast rules in the data center. Optimization is more about what works, and in today's high-density facility, that's ToR switches. By placing a switch at the top of each cabinet, data center managers significantly reduce the amount of cabling needed to link to each and every server. The ToR switch is closer to the equipment, and there are more of them per total IT load.

But ToR switches' true value lies in their flexibility. They can be deployed much more quickly than an EoR switch, which require individual cable connections to each and every server in that row. This isn't to suggest that ToR switches are the best option for all facilities and situations, but their inherent flexibility makes them the preferred choice for high-density data centers. 

So what's the catch?

One word: airflow. A switch per rack, as opposed to one or two switches per row, means there are more switches altogether, which can influence cooling capacity requirements. ToR switches must be operated at safe temperatures, since a failure of just one could take the entire rack offline. 

Problematically, though, many models of ToR switch (like the majority of IT equipment) need to be mounted backward so that connectors face the maintenance aisle, or hot aisle. This inhibits front-to-back airflow, which is crucial for regulating temperatures at the tops of racks – which also happen to be the hottest part of the rack, since it's farthest from the cool-air source.

An airflow facilitator with ToR switch and rack.Front-to-back airflow facilitators keep your equipment cool.

Re-directing air-flow orientation

The good news is that a ToR switch's airflow orientation can be manipulated. Specifically, hardware exists that can reorient airflow so that it maintains a consistent front-to-back cadence. These are low-footprint devices that can accommodate nearly any rack configuration. 

Rather than abandoning the flexibility enabled by ToR network switches, data center managers can instruct technicians to mount their equipment in any way that is most suitable for maintenance access, and allow a front-to-back airflow facilitator to do the rest. 

A final tip: Manage cables

"Streamline messy cable arrangements to avoid rack downtime"

The other big airflow inhibitor in general is improper cable management. Since every server in a rack needs to be connected back to the ToR switch, there's a risk that airflow will be stifled by a thick tangle of cables - that is, if they're improperly managed. 

In other words, bundle your cables together. All it takes is a few simple accessories such as plastic tubing, some twist ties, brackets, etc. Streamline your messy cable arrangements, and avoid rack downtime. 

Small mistakes can lead to big problems, but smart decisions will preempt them. 

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