When parallel option is used in expdp, it expects the DIRECTORY path to be available on nodes of the cluster. If you have created the directory on only one node and trying do the export using expdp, your export fails with the below error:

ORA-31693: Table data object "SCOTT"."EMPLOYEE" failed to load/unload and is being skipped due to error:
ORA-31617: unable to open dump file "/oracle_backup/scott_exp03.dmp" for write
ORA-19505: failed to identify file "/oracle_backup/scott_exp03.dmp"
ORA-27037: unable to obtain file status
Linux-x86_64 Error: 2: No such file or directory

Here is the resolution to fix this. Add the below parameter to your .par file resolve/bypass this issue:

CLUSTER=N

This is how your par file looks after adding the above parameter:

oracle@localhost cat scott_export.par
directory=EXPDP
dumpfile=scott_exp%U.dmp
parallel=4
logfile=scott_exp.log
job_name=scott_exp
schemas=SCOTT
cluster=N