I need to get an idea of how much WAL space will be required during a long (many hours) pg_basebackup over a relatively slow network connection. This is for a server that's not yet running PITR / streaming.
Any thoughts?
You may want to explore
--xlog-method=method
This will enable you to 'fetch' wals at end of backup (which means you should guess wal_keep_segment properly)
Or you can 'stream' them which means WALs will be backed up in parallel. This may introduce contention on network and hence may slow it down but you will not have to guess wal_keep_segment. See if this helps you.