Yeah I just set the archive_timeout to 5 minutes. But I thought that would make postgresql to generate more wal files than before. Because the wal files would be switched before getting completely full. So that would make more 16MB wal files with less than 16MB data, and that will increase the size of my backup. But after I changed archive_timeout and restarted the barman backup, it has not increased. So I wonder if I'm thinking wrong about it or I have done something wrong. Do you have any idea about this?
If the files are compressed, you will have more files, but the total size will be almost the same. Gzip compression reduces large sections of identical bytes to almost nothing.
For example, I just compressed a 750 MB file of zeros to 750 KB -- a 1000:1 compression ratio.