postgres backup strategies: https://www.postgresql.org/docs/current/static/backup.html https://www.hagander.net/talks/Backup%20strategies.pdf
continuous backup: https://www.postgresql.org/docs/9.6/static/continuous-archiving.html
streaming replication: https://www.postgresql.org/docs/9.6/static/warm-standby.html
http://dba.stackexchange.com/questions/133420/postgres-how-to-restore-backup-with-wal-eo
http://dba.stackexchange.com/questions/109444/backup-a-large-postgres-database-for-pitr