Assuming the scenario of equal number of DAG nodes at two datacenters(primary and DR) and users residing at third site.
Why is it that, MS is recommending FWS to be on a primary site instead of third site which can be a site where users reside for e.g.
In that later case, geo cluster can work in full swing with MNS cluster. If the users site, looses connectivity to primary datacenter but NOT the DR, the databases would be dismounted due to loss of quorum (due to MNS rules) at the primary site, and services would be up from the DR automatically. Is there any problem in reliability of exchange databases in that case ? or some particular problem with exchagne 2010 DAG architecture doing that ?
If we keep FWS on the primary site, automatic failover and resume of services at DR is not possible because of MNS, majority nodes rule.
Then ofcourse there would be manual work to brings things up at DR. It would not really be a geo cluster in that case. (i remember it would resemble to SCR in Exchange 2007 with less number of steps though)
Also DAC mode is also not required in this case i believe because of placement of FWS at third site.