Instead of writing my own script for backing up my OTRS installation i found a neat solution in the manual:
admin@support:~$ /opt/otrs/script/backup.pl -d ~/otrsbackup
Backup /home/entw/otrsbackup/2014-08-20_16-51/Config.tar.gz ... done
Backup /home/entw/otrsbackup/2014-08-20_16-51/Application.tar.gz ... done
Dump MySQL rdbms ... done
Compress SQL-file... done
admin@support:~/otrsbackup$ tree -A .
.
+-- 2014-08-20_16-51
+-- Application.tar.gz
+-- Config.tar.gz
+-- DatabaseBackup.sql.gz
1 directory, 3 files