# LASSi: Metric based I/O analytics for HPC

## TL;DR

LASSi is a tool that analyzes shared resource contention in HPC systems by using metric-based I/O analytics, helping identify performance variability and application slowdown issues.

## Contribution

LASSi introduces derivative risk and ops metrics for I/O behavior analysis, providing automated, holistic insights into filesystem and application performance in HPC environments.

## Key findings

- Metrics correlate with application performance variability
- Automated daily I/O reports for HPC systems
- Holistic analysis of filesystem and application I/O

## Abstract

LASSi is a tool aimed at analyzing application usage and contention caused by use of shared resources (filesystem or network) in a HPC system. LASSi was initially developed to support the ARCHER system where there are large variations in application requirements and occasional user complaints regarding filesystem performance manifested by variation in job runtimes or poor interactive response. LASSi takes an approach of defining derivative risk and ops metrics that relate to unusually high application I/O behaviour. The metrics are shown to correlate to applications that can experience variable performance or that may impact the performance of other applications. LASSi uses I/O statistics over time to provide application I/O profiles and has been automated to generate daily reports for ARCHER. We demonstrate how LASSi provides holistic I/O analysis by monitoring filesystem I/O, generating coarse profiles of filesystems and application runs and automating analysis of application slowdown using metrics.