In a top-of-rack data center architecture, DC teams install one or more switches in every rack of their deployment; despite the name, the switch doesn’t need to actually be at the very top of the rack. A ToR deployment keeps copper/Ethernet patch cables inside the rack, which helps with cable management. It also eliminates the single-point-of-failure that an EoR switch represents – if one ToR switch goes down for some reason, only the devices within that rack are affected, vs. the entire row. Another major benefit of EoR deployments is that each rack becomes a modular unit that DC teams can modify, upgrade, or scale without necessarily affecting other racks in the row.

On the other hand, a ToR deployment requires more switches than an EoR deployment, which can increase costs and complexity. More switches equate to more power draw, and they add an extra network hop to local traffic that could possibly affect throughput. Each switch must also be monitored, secured, and regularly patched, potentially creating more work for infrastructure teams. As a result, ToR deployments are also more challenging to scale, as each new rack added to the data center requires an additional ToR switch.

Comparing end-of-row vs top-of-rack deployments: Which should you choose?

 

	End-of-Row	Top-of-Rack
Number of switches	One or more per row	One or more per rack
Cable management	Requires patch cables running along the entire row	Keeps patch cables within the rack or cabinet
Cost	Fewer switches and lower power draw keeps costs down	More switches and higher power draw gets more expensive
Complexity	Fewer switches to secure, manage, and troubleshoot	More devices to manage
Ease of scaling	Can deploy an entire new row with only one networking cabinet	Each new rack requires one or more switches
Flexibility	Inflexible; networking changes affect entire row	Each rack is a modular unit that can be changed without affecting others
Resilience	EoR switch is a single point of failure for the entire row	One rack’s switch can go down without affecting any other racks

 

Both EoR and ToR architectures have advantages and disadvantages, with neither being the clear-cut winner for every possible use case.

End-of-row deployments are more cost-effective and easier to manage and scale, so they’re often favored by smaller, leaner IT teams or, on the opposite end of the spectrum, very large (or hyperscale) data centers. For example, a large cloud provider might prefer EoR to cut down on the number of switches to purchase, deploy, and manage at their hubs.

Top-of-rack deployments are modular, flexible, and resilient, which makes them a great choice for DevOps teams that need the ability to add or change components at any time without affecting the entire architecture. For example, managed service providers might prefer ToR so they can easily customize or update one customer’s rack without worrying about how the changes will impact others.

How Nodegrid improves resilience for EoR and ToR deployments

Nodegrid serial console switches can be deployed top-of-rack or end-of-row to improve the resilience of either architecture. Nodegrid switches connect to the serial port on data center devices to provide out-of-band (OOB) management, allowing teams to remotely manage and troubleshoot DC equipment even when the primary network is down. They isolate the management interfaces for data center infrastructure, making them inaccessible to malware or malicious actors on the production network. Plus, Nodegrid also provides network failover to keep business-critical services running during adverse events.

Nodegrid serial consoles have an open architecture that can integrate and host other vendors’ software and virtualized network functions. That means a single Nodegrid box could theoretically replace an entire rack of networking hardware, streamlining EoR deployments and making ToR architectures more feasible for lean, budget-strapped IT teams. Plus, Nodegrid switches and all connected devices can be remotely managed from a single, on-premises or cloud-based software platform, significantly reducing management complexity for either deployment.