Mellanox (NVIDIA Mellanox) MCX631102AN-ADAT Server Adapter Card in Practice

Mellanox (NVIDIA Mellanox) MCX631102AN-ADAT Server Adapter Card in Practice | RDMA/RoCE Low-Latency Transport and Server Throughput Gains

Background and Challenge: Network Bottlenecks Under Virtualization and Storage Pressure

An enterprise data center upgrading its access layer to 25GbE ran into a familiar set of performance tensions. In a virtualized cluster, storage traffic (NVMe over Fabrics and distributed block storage) shared the same physical links as business traffic, and the CPU overhead and microsecond-level latency jitter introduced by the standard TCP/IP stack caused throughput fluctuations on storage nodes during peak concurrency windows. Network engineers found that, in DPDK forwarding scenarios, the per-core processing capacity of legacy 10GbE adapters was already close to saturation, with a substantial share of CPU cycles consumed by network stack processing rather than by the workloads themselves.

The second challenge was fabric-level latency consistency. East-west traffic between compute and storage tiers had become the dominant traffic pattern, and the team needed a transport that could deliver low, predictable latency without sacrificing compatibility with the existing Ethernet fabric or requiring a wholesale shift to InfiniBand. The requirement was therefore not simply "more bandwidth" but a server-side endpoint that could combine 25GbE line rate with hardware-assisted RDMA/RoCE transport, offloading the data path from the host CPU.

Solution and Deployment: MCX631102AN-ADAT as the Server-Side Endpoint

The team selected the Mellanox (NVIDIA Mellanox) MCX631102AN-ADAT server adapter card as the standard server-side NIC for the upgraded fabric. Built on the ConnectX-6 Lx architecture, the MCX631102AN-ADAT ConnectX-6 Lx dual-port 25GbE SFP28 design provides two SFP28 ports per card, allowing one port to serve business traffic while the other carries storage or backup traffic, or both ports to be bonded for higher aggregate throughput and link redundancy.

Deployment followed a phased pattern. In the first phase, the MCX631102AN-ADAT Ethernet adapter card was installed in storage nodes and compute nodes within the same rack, connected to 25GbE top-of-rack switches. RoCEv2 was enabled on the storage data path, with PFC (Priority Flow Control) and ECN (Explicit Congestion Notification) configured to preserve lossless behavior for RDMA traffic while leaving business traffic on standard lossy queues. In the second phase, the same card was rolled out to additional racks, and the team verified that the NVIDIA Mellanox MCX631102AN-ADAT compatible with the incumbent hypervisor and operating system matrix without requiring driver rework.

Because the card supports 10GbE backward compatibility on the same SFP28 ports, older 10GbE switches could remain in service during the transition, which kept the migration incremental rather than disruptive. Engineers reviewing the MCX631102AN-ADAT specifications noted that the PCIe 4.0 host interface matched the current-generation server platforms, avoiding a host-side bottleneck that would have negated the gains from 25GbE line rate.

Results and Benefits: Lower Latency, Higher Effective Throughput

After the rollout, the most visible change was in storage access latency. With RoCEv2 carrying the storage data path, the host CPU no longer had to process the full TCP/IP stack for each I/O, and the team observed a marked reduction in tail latency during peak concurrency windows. The improvement was most pronounced in workloads with many small, concurrent I/O operations, where protocol processing overhead had previously dominated.

Effective server throughput also improved. By offloading the data path to the adapter, CPU cycles were returned to the applications, raising the achievable virtual machine density per host. The dual-port design gave the team flexibility to separate storage and business traffic onto distinct physical ports, simplifying QoS policy and reducing head-of-line interference between traffic classes.

The team also valued the operational side: a single SKU covering both storage and compute roles simplified sparing and firmware management. For organizations evaluating the MCX631102AN-ADAT price against the cost of a full fabric replacement, the incremental migration path and the reuse of existing 10GbE switching during the transition were significant factors in the business case. Teams that need the detailed feature matrix can consult the MCX631102AN-ADAT datasheet, and those comparing procurement options will find the part positioned as a mainstream 25GbE solution rather than a premium-tier component.

Summary and Outlook

This deployment illustrates where the MCX631102AN-ADAT Ethernet adapter card solution fits best: environments where east-west traffic dominates, storage and business traffic share a fabric, and the goal is predictable low latency rather than raw peak bandwidth alone. By combining dual-port 25GbE SFP28 connectivity with RoCEv2 hardware offload and 10GbE backward compatibility, the NVIDIA Mellanox MCX631102AN-ADAT lets teams raise server throughput and reduce tail latency without abandoning their existing Ethernet investment.

Looking ahead, as 25GbE becomes the default server access rate and RDMA/RoCE adoption expands from storage into AI inference and distributed data processing, the role of a capable server-side endpoint only grows. Architects planning the next fabric refresh can treat the MCX631102AN-ADAT as a building block that supports phased migration today and remains relevant as east-west traffic continues to climb.