We've set up an ADFS 2.0 server and 2008R2 RODC in a site together, and have enabled the RODC to cache passwords.
We expected ADFS to use the RODC that is located in the site with it.
We see in Resource Monitor that there is traffic from LSASS.exe to the RODC as we would expect, however we are also getting traffic from Microsoft.Identity.ServiceHost.exe to one of our writable DC's in another site.
Why are we seeing traffic to our other DC? We would have expected ADFS to talk to the RODC in the site with it.