HELP!!! The WAL Archive is taking up all space

Hi all,

Please help...

I have 1 master PostgreSQL and 1 standby PostgreSQL.
Both servers has the same OS Linux Debian Wheezy, the same hardware.

Both server hardware:
CPU: 24 cores
RAM: 128GB
Disk-1: 800GB SAS (for OS, logs, WAL archive directory)
Disk-2: 330GB SSD (for PostgreSQL data directory, except WAL archive
and except pg_log)

The part of the configuration are as below:
checkpoint_segments = 64
checkpoint_completion_target = 0.9
default_statistics_target = 10
maintenance_work_mem = 1GB
effective_cache_size = 64GB
shared_buffers = 24GB
work_mem = 5MB
wal_buffers = 8MB
wal_keep_segments = 4096
wal_level = hot_standby
max_wal_senders = 10
archive_mode = on
archive_command = 'cp -i %p /home/postgres/archive/master/%f'

The WAL archive folder is at /home/postgres/archive/master/, right?
This directory consumes around 750GB of Disk-1.
Each segment in the /home/postgres/archive/master/ is 16MB each
There are currently 47443 files in this folder.

If I want to limit the total size use by WAL archive to around 200-400
GB, what value should I set for the wal_keep_segments,
checkpoint_segments?

Regards,
Fattah