The Lustre filesystem serves as a vital element in high-performance parallel storage, meeting the rising demands of scientific, research, and enterprise environments. Widely deployed across HPC environments, ranging from small-scale applications in AI/ML, to domains like oil and gas, drug discovery, and meteorology, and manufacturing, Lustre addresses the universal challenge of efficiently accessing vast and ever-increasing volumes of data. Lustre is the filesystem of choice on six out of the top 10 fastest supercomputers in the world today, over 65% of the top 100, and also for over 60% of the top 500. Despite its widespread popularity, there is a lack of a complete and up-to-date reference, covering Lustre’s evolution, design, and various advancements made over the years. In this journal, we aim to fill this gap by providing a comprehensive journey of Lustre, including its history with significant contributions to HPC, detailed architecture and design elements, exploration of advancements added through its evolution, and future directions. Additionally, we present a comparison of Lustre with other prominent storage technologies of the era. To illustrate the current state of Lustre, we analyze several filesystem trends, including utilization, performance, and usage patterns on Orion, the Lustre filesystem on the first exascale supercomputer Frontier. We hope that this journal serves as a comprehensive educational reference for the current and future generations interested in HPC filesystem storage aspects.

Directory tree walks on parallel file systems are costly operations frequently required by many storage management tasks. Even listing the contents of a single directory can take minutes to hours for huge directories, as the tree walk performance of parallel file systems in Linux is severely throttled by sequentially accessing distributed metadata for each file through the syscall interface. We present eXtreme file attribute stat (Xfast), which scales the performance of directory tree walks by combining techniques that have been developed over a time frame of 10 years for the Lustre file system. Scalable statahead predicts file access patterns and prefetches required attributes, while the Size on MDT (SOM) mechanism reduces the number of RPC calls to collect file attributes. Xfast improves the performance of common directory operations, e.g. reduces the time to list one million files from 11 minutes to less than one minute for a single process.