SLURM

SLURM is the Simple Linux Utility for Resource Management and is an open source, fault-tolerant, and highly scalable cluster management and job scheduling system for large and small Linux clusters.

Slurm is fully integrated in our system. You do not need set any environment variables.

Partitions

A partition is a subset of the cluster, a bundle of compute nodes with the same characteristics.

Based on access restrictions our cluster is divided in different partitions. 'sinfo' will only show partitions you are allowed to use. Using 'sinfo -a' shows all partitons.

A partition is selected by '-p PARTITIONNAME'.

Partition	No. Nodes	Cores	Tot. Cores	RAM/GB	CPU	Remark
housewives	12	4	48	16	Dual Core AMD Opteron(tm) Processor 270 2,0 GHz
dfg	9	8	72	32	Quad-Core AMD Opteron(tm) Processor 2346 HE	Restricted access
dfg	8	8	64	32/64	Quad-Core AMD Opteron(tm) Processor 2376	Infiniband, Restricted access
dfg	8	12	96	32/64	Six-Core AMD Opteron(tm) Processor 2427	Infiniband, Restricted access
quantum	8	12	96	32/64	Six-Core AMD Opteron(tm) Processor 2427	Infiniband, Restricted access
dfg-big	3	32	96	128	8-Core AMD Opteron(tm) Processor 6128	Restricted access
dfg-big	3	48	144	128/256	12-Core AMD Opteron(tm) Processor 6168	Restricted access
dfg-big	4	64	256	128/256	16-Core AMD Opteron(tm) Processor 6272	Restricted access

The access to the DFG-Nodes (dfg and dfg-big) is restricted to the members of the SFB/TR49. If you do not belong to that group but want to test and develop programs for the Infiniband Network, please talk to the administrator. The access to the queue 'quantum' is restricted to group Prof. Hofstetter.

Submitting Jobs

In most case you want to submit a non interactive job to be executed in our cluster.

This is very simple for serial (1 CPU) jobs:

  sbatch -p PARTITION jobscript.sh

where jobscript.sh is a shell script with your job commands.

Running openMPI jobs is not much more complictated:

  sbatch -p PARTITION -n X jobscript.sh

where X is the number of desired MPI processes. Launch the job in the jobscript with:

  mpirun YOUREXECUTABLE

You don't have to worry about the number of processes or specific nodes. Both slurm and openmpi know about each other.

If you want infiniband for your MPI job (which is usually a good idea, if not running on the same node), you have to request the feature infiniband:

 sbatch -p dfg -C infiniband -n X jobscript.sh

Note: Infiniband is only available for the partitions dfg and quantum.

Running SMP jobs (multiple threads, not necessary mpi). Running MPI jobs an a single node, is recommended for the dfg-big nodes. This are big host, with up to 48 cpu's per node, but slow network connection. Launch SMP jobs with

  sbatch -p PARTITION -N 1 -n X jobscript.sh

Defining Resource limits

By default each job allocates 2 GB memory and a run time of 3 days. More resources can be requested by

  --mem-per-cpu=<MB>

where <MB> is the memory in megabytes. The virtual memory limit is 2.5 times of the requested real memory limit.

The memory limit is not a hard limit. When exceeding the limit, your memory will be swapped out. Only when using more the 150% of the limit your job will be killed. So be conservative, to keep enough room for other jobs. Requested memory is blocked from the use by other jobs.

  -t or --time=

where time can by "days-hours". See man page for more formats.

SLURM vs. SGE

This chapter compares the new batch system SLURM with the old SGE.

Partitions

Slurm has a slightly different view on the cluster. Nodes of a cluster are organized in partitions. To submit a job you have the choose one partition where to run the job.

Comparison of commands

The following table shows the most important commands in slurm compared to the commands of the grid engine.

Comparison of SGE and Slurm

SGE	Slurm	Description
qstat	squeue	Show running jobs
qsub	sbatch	Submit a batch job
qlogin	srun	Run interactive commands
qdel	scancel	Delete a batch job
qhost	sinfo	Get info about nodes
qmon	sview	Graphical Frontend

Parallel environments

Slurm has no concept of parallel environment. Slurm has been designed for parallel execution. This makes things easier, but gives your more responsibility when allocating cluster resources.

Memory Management

In Grid Engine you requested a hard limit for your memory, which should be higher than the estimated real memory usage. And second a virtual_free value which described your effective memory requirements.

In Slurm you specify only one parameter, which is the limit for your real memory usage and drives the decision where your job is started. The virtual memory of your job maybe 2.5 times of your requested memory.

Inline Arguments

sbatch arguments can be written in the jobfile:

#! /bin/bash
#
# Choosing a partition:
#SBATCH -p housewives

YOUR JOB COMMANDS....

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