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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

Doubts/Questions:

  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.

Thanks

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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.

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  • @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
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    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.
    – David Browne - Microsoft
    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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