pg_basebackup is taking more time than expected

Hi All,

We have database with the size of *425GB*. Out of this 425 GB, Around 40 to
60% of space occupied by the indexes. Ram allocated to this machine is
32GB and configuration parameters below.

max_connections = 800
shared_buffers = 9GB
effective_cache_size = 18GB
work_mem = 10MB
maintenance_work_mem = 1536MB
checkpoint_segments = 50
wal_keep_segments = 80
checkpoint_completion_target = 0.9
wal_buffers = 16MB
Max_prepared_transactions =0
synchronous_commit = on

In order to take the backup of the database we are using pg_basebackup
utility. But it is taking several hours (Around 18hours). Please guide me
what are the configuration parameters need to modify to reduce the time
taken by the pg_basebackup utility.

Is there any possibility to exclude the index data while taking the
pg_basebackup?

--
Regards,
Raghavendra Rao J S V
Mobile- 8861161425