Moving to Exchange DAG from single server

Hello Experts
Currently we have exchange 2016 CU6 installed on a single server. We have partitions as follows  
- OS and Exchange Installation on C
- Protocol and IIS logging on E Drive
- Mailboxes and Transaction Logs on E Drive, this drive is mapped to EMC storage. Hence no mailboxes data is stored on local disk.

Can someone please provide the step by step guide to migrate the current setup from single server to HA or DAG

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You simply provision one additional server, configure the SAME exact drive letters for the DB and LOGS and create a DAG.

Overall you should start from here:
cciedreamerAuthor Commented:
Thanks As you mentioned simply I will install exchange 2016 on another server with same CU version
However, I have got some queries

- Can I share the same Storage LUN with a new server or I have to create a Storage LUN with same size ?
- Is it necessary to have both servers with identical specs ?
- Is it possible to do active/passive scenario ?
You shouldn't share the same disk between multiple servers, unless you have a "layer" that's smart enough to provide appropriate synchronization between which machine access what resources and when.

Each server should have its' own dedicated LUN, so you would provision from the same storage, by the sound of it, a new LUN for the second Exchange server.

The MS recommended approach is to have the load, distributed equally, between all the nodes in the environment, based on amount of traffic, users, data, redundancy, etc. One of those recommendations is the have similar servers. Twins really.

If you choose, you can have active/passive state. Which means that all the Exchange databases are running from node1 and node2 there only for emergencies.
You might want that if you calculate, that running the second node with minimal parameters, to barely able hold the load if node1 goes down, is beneficial, until you bring backup node1.

However, the recommended approach is the divide the load. So whatever the amount of databases you have, you basically divide them between the servers, configure whatever settings needed in the DAG and every hour an automatic script will re-balance the databases between the servers.

So node1 holds 3 ACTIVE database copy and 2 PASSIVE ones, which simply means 3 databases to which users are connecting and 2 copies from the node2 of the databases that running active on it.

Vice-versa on the node2.
Active/Passive as requested.

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cciedreamerAuthor Commented:
Thanks Ronin for brief explanation

We need to setup Active/Passive scenario with Mailbox and CAS HA.
Once the Active nodes goes fail, node2 will be become active for databases  and for CAS we will just change the update DNS records manually and Firewall NAT rules.
cciedreamerAuthor Commented:
Just curios to know, in DAG how the election is done between Active/Passive nodes ?
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