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====== Use local storage on the compute nodes ======

If many jobs write to or read from the NFS server for the cluster home at the same time, the server can get very slow and even crash. Therefore it's very important that all users try to use local storage available to the nodes if possible. In most cases this will also speed up your jobs. In order to do so you have to tell the queuing system the amount of local disk space you want to reserve for your job. The queuing system will create a directory named ''/local_scratch/$PBS_JOBID'' on the nodes. After the computation has finished you must copy the results you want to keep from the local disks back to your home directory. Please try to copy only input and output files you really need, refrain from using ''*'' everywhere.
===== Example for TORQUE aka sheldon cluster =====

<code>
#!/bin/bash
#PBS -N local-file
#PBS -l walltime=1:00:00
#PBS -l file=10gb
#PBS -m bea -M dreger@physik.fu-berlin.de

# location of local storage directory on the node
local_dir=/local_scratch/$PBS_JOBID

if [[ -d "$local_dir" ]]; then
    echo "# found local storage at $local_dir. copying data from $PBS_O_WORKDIR to $local_dir."
    echo "# maximum file size is:" $(ulimit -f)
    # copy necessary input data
    cp $PBS_O_WORKDIR/input.dat $local_dir
    cd $local_dir    
else
    local_dir=
    echo "# no local storage found. running calculations in $PBS_O_WORKDIR"
    cd $PBS_O_WORKDIR
fi

# run jobs now
md5sum input.dat > result.out

# copy results back to $PBS_O_WORKDIR after job has finished
if [[ -n "$local_dir" ]]; then
    cp result.out $PBS_O_WORKDIR
fi
</code>

Example run using this jobfile:

<xterm>
dreger@sheldon:~/test-file> **ls**
input.dat  jobfile1
dreger@sheldon:~/test-file> **qsub jobfile1**
656781.torque.physik.fu-berlin.de
dreger@sheldon:~/test-file> **ls**
input.dat  jobfile1  local-file.e656781  local-file.o656781  result.out
dreger@sheldon:~/test-file> **grep ^# local-file.o656781**
# found local storage at /local_scratch/656781.torque.physik.fu-berlin.de. copying data from /home/dreger/local-file to /local_scratch/656781.torque.physik.fu-berlin.de.
# maximum file size is: 10485760
dreger@sheldon:~/test-file> **cat result.out**
aee97cb3ad288ef0add6c6b5b5fae48a  input.dat
</xterm>