The 'Link Speed' in 'nvswitch-cli' output refers to the effective bandwidth of the NVLink connection between the GPUs and the switch. A low value compared to the expected speed indicates a potential problem with the NVLink cables, their connections, or misconfiguration that's preventing the link from operating at its full potential. It is not related to memory clock, PCle, or NVLink protocol version but direct NVLink performance.

A distributed file system with data striping (option B) is the most effective because it parallelizes I/O operations across multiple storage nodes, reducing the load on any single storage device and improving overall throughput for many small files. RAID 0 (A) improves read/write speeds but offers no redundancy. Compression (C) can reduce storage space but adds overhead. Increasing block size (D) is beneficial for large files, but not necessarily for numerous small files. Tiered storage (E) can help, but distributing the file system is the priority for numerous small files.

For RDMA to function correctly, the necessary kernel modules must be loaded on both ends of the connection. These modules provide the core functionality for RDMA communication. While MTU and other network settings are important, the absence of the RDMA modules will prevent the connection from being established in the first place. Clock synchronization and TCP window size are less directly related to the initial RDMA connection failure. Power supply issues would likely manifest in other ways.

NVIDIA LinkX Direct Attach Copper cables support high-speed Ethernet and InfiniBand connectivity up to 400 Gbps, making them suitable for dense GPU cluster interconnects and short-reach data center links.

Inspecting the OpenSM log directly with grep is the appropriate way to check whether the subnet manager changed or recalculated routing behavior. Searching for routing-table related entries in the OpenSM log helps identify changes associated with the selected routing engine.