pg_basebackup can be called directly if you are using an identical filesystem layout on the target system. If this is not the case, pg_basebackup allows mapping the master's filesystem layout to the desired layout:
-T, --tablespace-mapping=OLDDIR=NEWDIR relocate tablespace in OLDDIR to NEWDIR
This holds true if I/O is not the problem (maybe because you are only managing a few gigabytes of data).