Platform Service Controller (PSC) can be deployed in different topologies, check the supported topologies here before deployment.

I have done a few deployments now using the below topology across two sites.

The following will illustrate how to check that replication between sites. Using this method provides Enhanced Linked-Mode between vCenters.

VMware KB can be found here

This example is using a Windows PSC. Open a command prompt and browse to the install directory - vmdird

First check the partners created

vdcrepadmin -f showpartners -h PSC-FQDN -u Administrator -w SSOadminpassword

Note here my second site PSC wis showing as a partner. Now run the same command the opposite direction

Now check the replication status

vdcrepadmin -f showpartnerstatus -h PSC-FQDN -u Administrator -w SSOadminpassword

You can then run this command the opposite direction. Follow the KB above if you need to create any new partners or delete any old partners.