SSO and AD Identity Sources in Multi Site Mode

I’ve installed a 2nd SSO server in Multisite mode for use at our DR site\VCenter with SRM.
Question: When I created the first SSO server I had to configure the Identity Sources for LDAP active dir looksup and that works fine but in the web client I cannot see anywhere to confirm the 2nd SSO server has the same sources.

My concern is that when I upgrade the DR VCenter to 5.1 and point it to the 2nd SSO server, it wont be able to resolve administrators defined by AD accounts. Or does the first SSO server provide all the details for all other SSO servers in multi site mode? Im not sure as you have to perform manual exports and imports for all SSO servers.

Thanks