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I'm trying to figure out how to make two Exchange Servers replicate.

My goal is to make that Exchange Mail keeps working even if one of the server fails or is for whatever reason unreachable.

They already talk to each other through AD and as far as I know most things are already replicating, except the Mailbox Databases. If a server goes offline, every Mailbox associated with it's Database becomes inaccessible.

So I did some research and apparently they should use one single Mailbox Database, replicated between them. But here is where the problems begin.

If I got this right I have to create a Database Availability Group, put the two servers in it, and set up a Mailbox Database Copy between them.

The problem is, apparently the Database Availability Group cannot be managed by a server in the group, it has to be a third one (called "DAG Witness")? What the hell.

Is there some way to workaround this? I don't want to have three servers, and to make matters worse the docs say the DAG Witness has to be a Windows Server too.

There must be some way to achieve this without having to rent an entire Data Center.

Havenard
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  • `They already talk to each other through AD and as far as I know most things are already replicating, except the Mailbox Databases` - That's probably an incorrect statement. If you didn't set up any HA then there isn't any HA. If you didn't set up a DAG then there is no DAG. Did you set up a DAG or HA? – joeqwerty Nov 01 '18 at 22:49
  • @joeqwerty Neither. As far as I can tell both DCs replicate settings to each other out of the box, including Mailboxes and Exchange Server settings, except the Mailbox Databases. Am I missing something? – Havenard Nov 01 '18 at 23:59
  • Mail related attributes of mail enabled objects are replicated as a part of AD replication, but that isn't and doesn't provide any HA for Exchange mailbox databases or mailboxes. You need to configure HA specifically for Exchange. – joeqwerty Nov 02 '18 at 01:51

1 Answers1

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This description is wrong:

The problem is, apparently the Database Availability Group cannot be managed by a server in the group, it has to be a third one (called "DAG Witness")?

You do need a Witness. However, it doesn't manage anything.

The Witness could be as simple as a share on third server. No extra software is needed. And a dedicated server is not required.

longneck
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  • But do they have to be in the Domain? And what happens if this file share goes offline? Can it be a Linux Server with Samba? – Havenard Nov 01 '18 at 20:23
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    Yes, it has to be in the domain. If the Witness goes offline and the two Exchange servers are still running, then nothing happens. But if the Witness is offline and one Exchange server goes offline, then the other Exchange server will not automatically bring the databases online. – longneck Nov 01 '18 at 20:27
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    You should read up on how Quorum works in Microsoft Failover Clusters. – longneck Nov 01 '18 at 20:28
  • I'm currently trying to figure out how I can get a Linux VM with Samba to do this role, before I go further do you know if it's possible or am I wasting time? – Havenard Nov 01 '18 at 20:57
  • Are you trying to give yourself indigestion? Forget it. What's the aversion to using a regular Windows server? You must have one somewhere else already. Even a share on a domain controller would be better than Samba. – longneck Nov 02 '18 at 00:55
  • It's a simple matter of resources, I can run a Linux with 512MB of memory in virtually any toaster, or can use one of the multiple VPS I already own for mail relay, while Windows Server 2016 needs 8GB min and that is with no roles installed. Besides, Linux boots faster, doesn't corrupt configuration files on power failure, there's a number of advantages of using it over Windows for Servers. – Havenard Nov 02 '18 at 01:30
  • Do you think I can do it without DAG? I'm reading about HA and apparently it requires no Witness. – Havenard Nov 02 '18 at 01:31
  • Never heard that use a linux server as a DAG witness server, as longneck suggested, you can select any existed server in your domain as a DAG witness server, it's more easier than studying how to use a Linux server as a witness server. – Niko.Cheng Nov 02 '18 at 08:14
  • You obviously don't like Windows. Take off your blinders and acknowledge that I said you can use ANY other domain joined Windows server. – longneck Nov 02 '18 at 13:08
  • @longneck I love Windows, I wouldn't use anything else. On my personal PC. For Servers it blows, a simple power loss can corrupt it beyond repair, it's pathetic. Been there a ton of times. Even when it still boots it is never the same, hangs on shutdown, services fail to initialize automatically or things like that. It's like if anything goes wrong at all it leaves a scar for life. If it wasn't for Exchange I would stay far away from it. – Havenard Nov 02 '18 at 19:19
  • @longneck Just last week I had a server completely lose the ability to manage it's own DNS server after a power loss, spent 12 hours on the problem, it was beyond fixing, any interaction whatsoever with the DNS server was greeted with Access Denied. Luckily I had a backup, had to restore the entire server. Fun times. – Havenard Nov 02 '18 at 19:30