What is the advantage to use archive_mode = always in a slave server compared to archive_mode = on (shared WAL archive) ?
I only see duplication of Wal files, what is the purpose of this feature ?
You might not have a shared wal archive in the first place. For example, your only access to the master is through the streaming replication protocol, but you want to maintain a local WAL archive anyway so you can PITR locally for testing or debugging purposes.
