I am going to set up AG's for the very first time, so with little or no experience, please guide me on below understanding:

If i am setting up 4 node AOAG with below scenario:

Node1-NY Data Center - Primary replica

Node2-NY Data Center - Secondary replica

Node1---Node2 Synchronous mode

Node 3 - Michigan Data Center secondary replica acting as DR site with different subnet with ASYNC mode

Node 4 -- Readable secondary in NJ data center for reporting purpose using ASYNC mode


  1. In above Multi Subnet configuration can i still use a different storage across 4 nodes or do i need to use SAN replication as i have read few blogs and confused if that is a requirement for multi site env

  2. What should be ideal Quorum setup? -- Can i have that in NJ site as file share witness?

Also if there is better design than above, please suggest as i have never implemented or worked on AOAG before.

RPO/RTO for critical apps varies between 2 hrs to 4 hours

While for mid critical its between a day and 2

I can add up information as needed.


1 Answer 1


This is generally a consulting engagement since there are lots of minutiae. But to answer your techincal questions:

  1. The AG handles the data synchronization process. There is no storage-based replication needed or involved with AGs whether it is local or multi-site.

  2. You can use the NJ site as a FSW, but arguably the best option for multi-subnet in WS2016+ tends to be cloud witness.Figuring out the right witness for quorum needs a bit more informaiton about your infrastructure, which is again, generally a much deeper consulting engagement.

Also, it's not AOAG. Just AG. Always On (which has a space) is just a marketing umbrella term which covers both AGs and FCIs. The ON is not captialized.

  • @Thanks Allan. I will look into that option. Also is there specification for hearbeat connection setup as well. I am aware in FCI being setup as two different ones, is there a change for AG?
    – Newbie-DBA
    Mar 23, 2019 at 20:09
  • 1
    I would just configure a file share witness in New York, as there are no remote synchronous replicas, and you (sensibly) are not trying to get automatic failover except inside the New York site. Mar 23, 2019 at 23:59
  • @DavidBrowne-Microsoft- Thanks for the suggestion. Also currently in my lab for similar scenario of 4 nodes i have dynamic quroum set up that is no witness which seems to be taking away vote as intended, For 4 nodes do you think Setting up file share witness still holds true and for which failed case?
    – Newbie-DBA
    Mar 24, 2019 at 20:15

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