[GENERAL] Chained slaves smaller?

Hi,

I have SR set up in a couple of datacenters, where there’s a master in DC_A with 2 slaves, and a 3rd slave off that
masterin DC_ B. Also, in DC_B I have 2 slaves chained off the “local master”. Our main database is ~551GB in DC_A and
onthe replica in B that is subscribed to the real master. However, on one of the chained slaves in DC_B that database
isonly 484GB. The only thing different about this smaller slave is that it was created by taking a basebackup from the
“localmaster” in DC_B rather than sucking it over the WAN from the true master in DC_A.  

This makes no sense to me since I thought SR replicas are bit for bit copies, so I’m somewhat concerned. Any ideas how
thiscould be? 
—
Jon Erdman
Postgres Zealot