Backup Copy of a Production server.

List,

I am in need to copy a production PostgreSQL server  data( 1 TB)  to  an external storage( Say USB Hard Drive) and need to set up a backup server with this data dir.

What is the trivial method to achieve this ?? 

1. Is Sqldump an option at a production server ?? (  Will this affect the server performance  and possible slowdown of the production server ? This server has a high IOPS). This much size 1.2 TB will the Sqldump support ? Any bottlenecks ?

2. Is copying the data directory from the production server to an external storage and replace the data dir  at a  backup server with same postgres version and replace it's data directory with this data dir copy is a viable option ?

# cp  -r   ./data  /media/mydb_backup  ( Does this affect the Production database server performance ??)   due to the copy command overhead ?

OR  doing a WAL Replication Configuration to a standby is the right method to achieve this ?? 

 This is to take out the database backup outside the Datacenter and our DC policy won't allow us to establish a network connection outside the DC to a remote location for WAL replication .

Any hints most welcome ..

Thank you

Krishane