Adding Exchange Server to a DAG - new DC

Question

This Question is not for error finding, this is for generic guidance to add a new exchange server in a new DAG as not much information is available on internet.

I have a standalone multi-role exchange 2016 in my dc. We are planning to make this a highly available infrastructure and Host the secondary to a different DC. Basically keeping primary and secondary exchange in 2 different datacenters.

Could someone let me know the possibilities and difficulties ..and advice in the setup. i have to host an Active/Active exchange DAG in 2 servers that are geographically away.

Consideration for the setup.

Exchange 2016, one in primary location another in secondary location.

Internet speed BW 10mbps between the datacenters. latency is less than 100ms

Single AD at primary location, planning for L2 VPN to extend the VLAN

LB, mostly Microsoft NLB hosted at primary site, having both exchange managed under same pool in primary site.(also considering Netscaler as LB for CAS Role as teh sites are geographically far)

If a different LB needs to be used, please suggest.

OWA will be used.

Outlook Client will be used Office 2013/2016.

User count : 250+

We need to set up Active/Active DAG with mailboxes in both servers in 2 separate data-center.

Thanks //PASHa

Answer 1

At first your knowledge regarding Exchange seamed to be very low (but that might be only my impression). You are running an NLB with Exchange 2016 which isn´t supported by Microsoft with Exchange 2016. Then you wish to setup an active / active Exchange server with 2 server which isn´t working. An active / active exchange environment would mean you have 4 Exchange server in use (two in one DC, where one is active and the other one is passive) added to one DAG. This is due to the reason that if you have a DAG with two exchange server a mailbox can be only active on ONE Exchange server and not two. Additional it seamed you do not know that you need to come up with a clever plan for an witness server to avoid that the Exchange server do not know which one is active and which one is passive due to the reason that the witness is no longer accessible due to a network cut.

So based of that here is the information for a Exchange DAG with 2 Server (Active / Passive) as your "design approach" will not work.

1. st point: When you use a NLB (as outlined in your question) you need to change that to a different technology (e.g. an Hardware LoadBalancer) at first. Because Windows Network Load Balancing (NLB) will not be supported against Exchange 2016 for the simple reason that Windows Failover Clustering and Windows NLB cannot coexist. Therefore, a third-party solution must be deployed. For more info's see the official Microsoft documentation. For 250 users you might wish to start using an cost free software load balancer (e.g. one from KEMP).

2. nd point: Once the 2nd Exchange server is up and working and once you have setup the MAPI over HTTP balancing (Exchange 2016 do not suppot plain MAPI) you need to decide how you wish to deal with incoming emails. That means if you wish to add an 2nd MX record or if there is an mail hoop in front of your environment which can do the job. You can also route the emails to only one Exchange server if you prefer. As you didn´t specify that point in your design setup I assume here that this would be done by a 3rd party hoop e.g. an AntiSpam/AntiVirus gateway.

3. rd point: You need to decide how you wish to load balance the environment. Should the new Exchange server act only as a kind of failover or did you plan to mount the user DBs across the server? Depending on the mailfile size and traffic (which we do not know) the 10M line might be to small. Keep noted that a DAG with 2 Exchange server can be only active / passive as outlined above. So you might wish to replica the content into a 2nd DC and once the 2nd DC is down you might then use the 2nd former passive Exchange server. Or you might come to the conclusion to activate only 50% of the active DBs on one Server and the other 50% of the DBs on the other server. However this depends on your overall setup (e.g. see backup and MX question here) and your users.

4. rd point: You need to decide how to backup the DBs. Some backup environments can only backup active DBs so you might pick up an HA which fits your backup environment or need to do some scripting to change the mounting on the weekend when you run a full backup over all active DBs.

5. rd point: I highly recommend to use the Exchange calculator which will help you to understand if the network line fits your environment. You need to enter multiple info's here which we do not know as you didn´t outlined them (e.g. how many traffic you expect inter side between the both servers).

6. rd point: Build a DAG, adding the 2nd Exchange server and moving the DBs inside the DAG is quite easy and might be the reason why you couldn´t find some info's here.

7. rd point: Keep noted that you need a witness server here. This server might be in one DC, however if that one is down the Exchange server couldn´t contact that one any longer. The preferred way would be to host that in a 3rd DC (e.g. some pick up Microsoft Azur here).

Conclusion: Compared to the fact that you have a very low amount of users I would say the 10M is OK. But if you have very big mail file or a lot of shared mailboxes this might be different. Additional and based on your Exchange experience I would highly recommend that you hire an Exchange consult.