A company has built a high performance computing (HPC) cluster in AWS for a tightly coupled workload that generates a large number of shared files stored in Amazon EFS. The cluster was performing…

For tightly coupled HPC workloads, launching the cluster within a single Availability Zone minimizes network latency between instances, which is critical for achieving maximum performance for inter-node communication.

Attaching elastic network interfaces in multiples of four is not a standard or specific performance optimization for HPC; network interface configuration is generally driven by throughput requirements rather than fixed numerical multiples.

Elastic Fabric Adapter (EFA) provides high-throughput, low-latency network communication for EC2 instances, making it ideal for tightly coupled HPC applications that rely heavily on Message Passing Interface (MPI) or similar communication protocols at scale.

Spreading a tightly coupled HPC cluster across multiple Availability Zones introduces higher inter-instance network latency, which degrades performance for workloads that are sensitive to communication overhead.

Amazon EBS volumes are block storage attached to individual instances and cannot inherently provide a *shared* file system across 1,000 EC2 instances for 'a large number of shared files'; this would require a fundamental re-architecture of the storage model.

Amazon FSx for Lustre is a high-performance file system optimized for compute-intensive workloads like HPC, offering significantly higher throughput and lower latency than Amazon EFS, which can become a bottleneck for very large clusters with intense I/O demands.