HP XC System 4.x Software LSF-SLURM External Scheduler, How LSF and Slurm Launch and Manage a Job

request more than one core for a job. This option, coupled with the external SLURM scheduler, discussed in “LSF-SLURM External Scheduler”, gives you much flexibility in selecting resources and shaping how the job is executed on those resources.

LSF reserves the requested number of nodes and executes one instance of the job on the first reserved node, when you request multiple nodes. Use the srun command or the mpirun command with the -srunoption in your jobs to launch parallel applications. The -sruncan be set implicitly for the mpirun command; see “Submitting a Parallel Job That Uses the HP-MPI Message Passing Interface” for more information on using the mpirun -sruncommand.

Most parallel applications rely on rsh or ssh to "launch" remote tasks. The ssh utility is installed on the HP XC system by default. If you configured the ssh keys to allow unprompted access to other nodes in the HP XC system, the parallel applications can use ssh. See “Enabling Remote Execution with OpenSSH” for more information on ssh.

The following table shows exit codes for jobs launched under LSF integrated with SLURM:

Table 10-1 LSF with SLURM Job Launch Exit Codes

Exit Code	Description
0	Success
124	There was a job launch error in SLURM
125	There was a job launch error in HPC-LSF

10.7 LSF-SLURM External Scheduler

The external scheduler option is an important option that can be included when submitting parallel jobs with LSF integrated with SLURM. This option

•Provides application-specific external scheduling options for jobs capabilities

•Lets you include several SLURM options in the LSF command line.

For example, you can submit a job to run one task per node when you have a resource-intensive job that needs to have sole access to the node's full resources. If your job needs particular resources found only on a specific set of nodes, you can use this option to submit a job to those nodes.

The LSF host options enable you to identify an HP XC system "host" within a larger LSF cluster. After the HP XC system is selected, LSF's external SLURM scheduler provides the additional flexibility to request specific resources within the HP XC system

You can use the LSF external scheduler functionality within the bsub command and in LSF queue configurations. See the LSF bqueues(1) command for more information on determining how the available queues are configured on HP XC systems.

See “Submitting a Parallel Job Using the SLURM External Scheduler” for information and examples on submitting jobs with the LSF-SLURM External Scheduler.

10.8 How LSF and SLURM Launch and Manage a Job

This section describes what happens in the HP XC system when a job is submitted to LSF. Figure 10-1illustrates this process. Use the numbered steps in the text and depicted in the illustration as an aid to understanding the process.

Consider the HP XC system configuration shown in Figure 10-1, in which lsfhost.localdomain is the virtual IP name assigned to the LSF execution host, node n16 is the login node, and nodes n[1-10]are compute nodes in the lsf partition. All nodes contain two cores, providing 20 cores for use by LSF jobs.

92 Using LSF