The HPC Triangle

The HPC triangle describes the three resources every HPC cluster needs in balance: fast compute, fast storage, and fast networking. Because each of these can easily bottleneck the other two, the performance a cluster actually delivers is set by whichever corner is weakest, not by any single component in isolation. The concept is analogous to the classic "cheap, fast, good" triangle, and it makes clear why designing a supercomputer is a balancing act rather than a matter of buying the fastest processors.

The three corners of the HPC triangle

• Fast compute, Provided by CPUs, GPUs, FPGAs, and other accelerator cards, this is where the actual calculations of a computational job happen. It lives on the cluster's compute nodes.
• Fast storage, Provided by parallel file systems, storage tiering, and fast underlying media such as SSDs, this supplies a file system that jobs can read from and write to quickly.
• Fast networking, Provided by an HPC interconnect, this links the compute together so job data can be communicated across the cluster, and it usually connects the storage to the compute as well.

Why balance matters

The three corners are interdependent. Powerful processors sit idle if storage cannot feed them data fast enough; a fast file system is wasted if the interconnect cannot move that data to the nodes; and a fast network delivers little value if the compute cannot keep up. This mutual dependency is what makes cluster design and planning complex: money spent on one corner yields little if another corner is left behind.

Corner	Provided by	Job it does
Compute	CPUs, GPUs, FPGAs, accelerators	Performs the calculations
Storage	Parallel file systems, tiering, SSDs	Reads and writes job data
Networking	HPC interconnect	Moves data between compute and storage

Understanding the HPC triangle is the starting point for sizing a cluster: a well-designed system keeps all three corners in proportion so that no single resource strangles overall throughput.