Re: Pgbackrest setup for two sites with limited bandwidth

What you are asking for is tricky, but possible. You can setup two repos,
one for each server. On the first server (in datacenter A), you have a
"normal" pgbackrest configuration, with an explicit backup-standby=n. pg1-*
points to the local server, pg2-* points to the replica. The repo is in
datacenter A.Backups run from PG server in datacenter A, to the backrest
repo in datacenter A. WAL is archived from A -> A

On datacenter B, you have a separate local repo, a different stanza name,
and within that stanza, you have backup-standby=y, pg1 pointing to the
local pg, pg2 pointing back to A. In the postgresql.conf, your
archive-command pushes to this second repo, and archive_mode is "always".
Backups run from the PG server in datacenter A, but 99% of the files are
actually copied from the replica in datacenter B, and goes to the backrest
server in datacenter B. WAL is archived from B -> B.

That's the basic idea. It falls apart rapidly if this second data center
ever fails over.
Cheers,
Greg

--
Crunchy Data - https://www.crunchydata.com
Enterprise Postgres Software Products & Tech Support