Setting Up Cascading Standby

Running Pg 9.2 on CentOS. Currently have a standard primary/standby setup,
with the standby in a different DC across the country from the primary.
These are all on VMs.

We want to add another standby in the same standby DC. What I'd like to do
is have the current standby become a cascading standby, and restrict user
queries to the new hot standby (and/or any others we hang off of it). But
the soon-to-be-cascading standby would be strictly for DR and cascading
WALs.

The docs and articles I've read seem to focus heavily on the streaming
replication aspect of things. But I imagine we want to also have WAL files
getting copied downstream as well. I'm writing to ask how the pros from
Dover handle this. Custom script in place of archive_cleanup_command on the
cascading standby to push the archived files downstream before deleting
them? Or some rsync job on the cascading standby running every minute to
push changes downstream?

Don.

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Don Seiler
www.seiler.us