Stretching sql across two datacenters with a multi subnet cluster and SQL always on availability groups and a 3rd location for file share witness. How many cluster nodes is recommended two in each datacenter so four total? Primary DB in primary Datacenter with secondary readable replicas with synchronous commit with a multi subnet listener ? Also is it recommended to leave the DDCs in each datacenter in the primary zone or have seperate zones for each Datacenter? I presume alot depends of the connectivity between datacenters latency/bandwith... ive also looked at the powershell command set-configsite -primaryzone to set the secondary zone as primary if primary zone is down. I much prefer seperate XDsites in each datacenter and use storefront aggregation and user mapping and Netscaler OGR but not a option unfortunately