What is SLURM?

SLURM is an acronym for Simple Linux Utility for Resource Management

SLURM is a free and versatile tool that streamlines job scheduling and resource allocation on Linux-based clusters. Imagine having dozens or even hundreds of compute nodes – SLURM ensures efficient utilization by:

• Resource Allocation: Granting users exclusive or non-exclusive access to compute nodes for specific durations.
• Job Scheduling & Execution: Providing a framework for launching and monitoring jobs, often involving parallel processing techniques like MPI (Message Passing Interface).
• Queue Management: Maintaining a queue of submitted jobs, prioritizing them based on predefined rules, and ensuring fair access to resources => Resource contention

Why use SLURM?

• SLURM is an open-source Job Scheduler for small and large linux clusters and unix-like kernels
• SLURM is fault-tolerant and highly scalable cluster management system
• SLURM is relatively self-contained with the components it needs to run

What are Important components of SLURM?

• slurmctld, the central controller monitoring all the compute nodes that are registered as part of the cluster. Typically this is run dedicated management node
• slurmd, the daemon that runs on each compute node

Picture Source: https://slurm.schedmd.com/arch.gif

What are different entities in SLURM ?

• Nodes - Actual Compute nodes
• Partitions - Logical grouping of nodes a.k.a Job Queues with an mix of constraints (job size limit / job time limit), priority
• Jobs - Allocations of resources assigned to a user for a specified amount of time. Logical groups of job steps
• Job Steps - sets of tasks with in a job. Typically there are parallel tasks

Picture Source: https://slurm.schedmd.com/entities.gif

Finally the list of important commands

Ordered in the most frequently used or relevant

• sbatch - to submit a job for eventual execution
• srun - submit job for execution in real time. It could even be used to initiate job steps in real time
• scancel - to cancel a pending or running job step or job (all job steps)
• squeue - state of jobs/job steps
• sinfo - show the state of partitions and nodes as report
• sview - GUI to display information for jobs/parititions and nodes
• sstat - info about resource utilization by a running job/job step
• sshare - info about fairshare usage. Only available in conjuction to priority/multifactor plugin
• sprio - details of the factors/components/constraints affecting a job's priority
• scontrol - admin tool to view/modify the state of slurm
• sbcast - transfer a file between local storage on nodes with in a job allocation. This works like in a p2p fashion and simulates diskless nodes and improved performance relative to shared FS
• sattach - attach stdin / stdout / stderror along with sending signal to an already running job
• salloc - allocate resources in real time to the jobs. This spawns a shell with allocated resources and srun commands with in this shell is used to launch parallel task
• sacct - report job or job step information about active/completed jobs

Recommended exercise to go through SLURM demo on EC2 instance SLURM demo on AWS Ubuntu 22.04 EC2 instance