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The ior application is MPI enabled and befits by calling the command using the srun ior. Calling srun ior will spawn the same number ofior clients as tasks across the number of nodes requested in salloc or sbatch. Using srun ior -N=<tasks> will limit the number of ior clients that will participate in the test to the number specified to the number that the flag is called with. The default behavior of srun ior is to have all ior clients to participate in the test. The application uses the number of cores allocated to the tasks for spawning threads to perform the test. See ior --help for more informationthus requires to be called with srun from the command line.
When called, ior will spawn as many clients as mpi tasks requested by the job: e.g. nodes x tasks-per-cpu or ntasks.
Using the -N=<tasks> option you can limit the number of clients that are actual run to the value of <tasks>. See ior --help for more information.
For example:
| Code Block |
|---|
# Total of 6 tasks
#SBATCH --nodes=2
#SBATCH --tasks-per-node=3
# Default behavor: Spawn and run 6 ior clients:
srun ior
# Spawn 6 ior clients, but only run 2:
srun ior -N 2
# The ior application decides on which nodes/tasks the clients run from. |
If you define --cpus-per-task=x as a job option, then each ior client will run with x number of threads.