Data center cabling, EoR, MoR, or ToR?

As data centers continue to grow in size and complexity, new approaches to network cabling are emerging to meet the demand for higher performance, lower latency, and greater scalability. To satisfy massive servers connection requirements, the access switch usually is set in three architectures: End-of-Row EoR and Middle-of-Row MoR and Top-of-Rack ToR.

End-of-Row 

End-of-Row architecture, also known as end-of-row switching, switches are placed at the end of each row of server racks in the data center. In this architecture, servers in each row are connected to the switch at the end of the row, which is then connected to a core switch or router that provides connectivity to other parts of the network.

Advantages.

Fewer switches to manage, hence lower switch cost and maintenance costs.

Fewer prots required in the aggregation.

Cost-effective compared to the top of rack(ToR)

Disadvantages

Because switches are located at the end of each row, the maximum distance between switches and servers is limited, which can impact latency and throughput.

Massive cables required, more infrastructure required for patching and cable management.

Difficult to maintain.

Upgrades is not convenient, it affects the entire row.

Middle-of-Row 

Middle-of-Row architecture, also known as middle-of-row switching, switches are placed in the middle of each row of server racks. In this architecture, servers in each row are connected to a ToR switch located in the middle of the row, which is then connected to a core switch or router that provides connectivity to other parts of the network.

The major difference between EoR and MoR is that since the switches are placed in the middle of the row, the cable length is reduced. Rest of the terminologies will remain the same as EoR.

Top-of-Rack

ToR switches are switches that are located at the top of each server rack, providing connectivity to the servers within the rack. ToR switches are typically high-density, low-latency switches that provide high-speed connectivity to the core network.

Advantages

ToR switches simplify cabling and management, as each server is connected directly to the switch located within the same rack. No large copper cabling infrastructure required.

Low cabling cost.

Excellent scalability.

Easy to upgrade.

Disadvantages.

It requires a significant amount of power and cooling, which can increase operating costs.

It will also be more difficult to manage and troubleshoot, as there are many switches to maintain.

Probably causing port waste.