The Move to the cloud is in many cases not a binary switch but more a graceful journey (hopefully), and in many cases a hybrid cloud situation is desirable especially for Exchange and office 365 with ADFS.
Indeed a hybrid cloud situation of course has other benefits such as reducing the exposure to the cloud provider both in terms of availability/technically but also commercially, and as such in many cases it is the preferred architecture as opposed to simply a cloud migration stop gap.
Many organisation’s are opting for a dual data centre setup in Active Active or Active passive using GSLB – (Global Server load balancing) between the sites. A dual data centre setup can also be used between multiple clouds, and or a combination of clouds and on premise.
The example below is a simplified setup of running an Active Active multiple data centre setup for Load balancing exchange in a hybrid exchange office 365 setup.
It’s important to use a load balancer for hybrid exchange with office 365 as the ADFS server must be available to Office 365 to authenticate the users.
Once the user is load balanced with GSLB to a data-centre the internal edgeNEXUS load balancers can also be used to load balance the mailbox traffic as well as between multiple internal ADFS servers.