Exchange 2019 on Prem redundancy

Island3r 1

Hi Everyone..

I have a customer who would like to use on prem Exchange 2019 but also have redundancy/high resilience in case that server failed.

They have around 100 mailboxes / 70 Active Directory users. We have two identical servers with decent spec capable of running Exchange 2019.

The existing environment has two Server 2019 DC's and another Server 2019 member server running a few different network applications.

My question is how would you go about achieving this?

Would you have the two servers configured as DAGs and use one of the DC's and the witness server or is there another way?

Any input would be greatly appreciated, thanks :)

Yuki Sun-MSFT 40,856 Reputation points

2021-08-31T08:53:48.2+00:00

Hi @Island3r ,

It has been a while and I am following up to see how things are going on with this thread. If you still have further concern on this, feel free to post back.

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3 answers

Andy David - MVP 141.3K Reputation points MVP

2021-08-24T18:27:49.723+00:00

If you want server HA within the same physical location, I would have have 3 Exchange Servers in one DAG.

I would recommend 3 servers in the DAG so you can bring one down for maintenance and still have redundancy. If you have 3 servers, then there is no need for a File Share Witness.
If you can only have 2 Exch Servers in the DAG, then The File Share Witness should not be on a DC. Use the member server if that is all you have.
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Island3r 1 Reputation point

2021-08-24T18:51:14.207+00:00

Thanks for the quick reply Andy.

Unfortunately we only have the two servers at the moment but a third could be something to look into/invest in in the next budget. Thanks for the advice on the Witness as well.

Can you see any other method (apart from M365, my customer is not ready for that move even though I've given them the hard sell). We're in a remote area of the world where replacement servers could take up to 3 months to arrive so having the best HA as possible is the objective.

Yuki Sun-MSFT 40,856 Reputation points

2021-08-25T09:04:21.2+00:00

Hi @Island3r ,

Would you have the two servers configured as DAGs and use one of the DC's and the witness server or is there another way?

Technically this configuration can be realized. The DAG requires a minimum of two members to provide high availability and according to Witness server requirements, "The witness server can be any computer running Windows Server.", which means a DC is qualified to play as the withness sever.

However, based on what I've read, agree with Andy that using a DC for a file share witness is not a recommended practice. Below is a blog I found which also emphasized not doing this in production:
How to use a Domain Controller as an Exchange 2013 DAG Witness Server (Don’t)
(Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.)

Taken in the round, having two Exchange servers (no DAG) with one DC could be a safer option at this point of time. After the additional server is introduced, you can then set up the DAG.

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Limitless Technology 39,351 Reputation points

2021-08-25T10:28:30.3+00:00

Hello Island3r,

When talking about HA and resilience deployments there is no easy answer, and that is for a good reason. To ensure that all the components are set up in the correct way to ensure the perfect functioning.

I will recommend you the next literature and select what is convenient for the size of this deployments:

https://learn.microsoft.com/en-us/exchange/high-availability/plan-ha?view=exchserver-2019
https://learn.microsoft.com/en-us/exchange/high-availability/deploy-ha?view=exchserver-2019

Hope this helps!

Luis P
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Limitless Technology 39,351 Reputation points

2021-08-25T19:02:09.947+00:00

Hello @Island3r ,

Additionally,

I would also suggest you to also consider your Exchange servers hosted in virtual environment on Hyper-V Host and then configure failover clustering of Exchange VMs , this would also give flexibility for resources and backing up as well.

As you have 100 Mailboxes so that it would not take much resources for exchange VMs.

If the reply was helpful, please don’t forget to upvote or accept as answer.

Thanks, Prakash

Andy David - MVP 141.3K Reputation points MVP

2021-08-25T19:33:44.033+00:00

You don;'t want to configure any clustering failover technology outside of the built-in Exchange clustering.
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Andy David - MVP 141.3K Reputation points MVP

2021-08-25T19:15:45.127+00:00

I would say, if you stick with 2 servers, then put the FSW on a vm guest you build new or on the existing member server. With your current limitations, that will work and provide HA.
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