Is it possible to remain protected against a full Exchange server failure if you have two sites and only two Exchange servers?

Here is the configuration:
Two Exchange 2013 servers with CU8 each running MB and CA. EXCH-Prod (192.168.10.10) is in Site1 and EXCH-DR (192.168.20.10) is in Site2. All URLs are configured to use mail.company.com. There are two DNS records for mail, one for 192.168.10.10 and another for 192.168.20.10. There are also two autodiscover records pointing to those same IP addresses. Outlook 2013 autoconfigures and connects through Outlook Anywhere at mail.company.com. All Outlook clients are located in Site1. The two servers make up a DAG with one mailbox database MB1 where all the mailboses are located.

Question: Is it correct to say that EXCH-Prod goes offline then Outlook should reconnect automatically to EXCH-DR? I'm getting mixed results in testing and am getting mostly failures that look like a Client Access issues; but if Outlook proxies through mail.company.com then I don't know why that would be.

Test results: Everything works fine if I activate MB1 on EXCH-DR then move it back. If I activate MB1 on EXCH-DR then disconnect the network adapter on EXCH-Prod Outlook disconnects then reconnects about a minute later. If I activate MB on EXCH-DR then shutdown EXCH-Prod Outlook disconnects and never reconnects; I waited 5 minutes. If I shutdown EXCH-Prod without moving MB1 it automatically moves itself but Outlook never reconnects. If I close Outlook, shutdown EXCH-Prod, then Open Outlook it takes about a minute then connects.

Any thoughts on this would be appreciated. Thanks in advance.

-Jeff

Hello,

Thank you for your post.

This is a quick note to let you know that we are performing research on this issue.

Hi Simon,

Thanks.

Quick update: I ran the "shutdown EXCH-Prod without moving the active database" test again in a freshly built virtual lab. I watched the database activate on the DR server after a minute or two but Outlook took a very long time to reconnect. I would guess it took at least 30 minutes if not more. I did not install CU8 for this one; just a fresh install of Exchange 2013.

I look forward to hearing any input you may have on this.

Thanks again.

Hi,

In your environment, there are two sites, and only one server(CAS&MBX) in each site. It is not recommended for High Availability. Once a server is down, the whole site is down.

Please notice that there would be a big delay between the AD servers in the two sites. Once one site is down and we have to put another site online, it requires a little long time for AD replication between the sites, which would definitely affect the Outlook clients reconnection. (If Outlook has been trying to connect to an Exchange server however it still cannot connect, it may not keeping trying. It would shows as disconnected until we restart Outlook application.)

Actually, the while site down is definitely the extreme scenario.

To the Exchange high availability, it is recommended to have at least two CAS servers and two MBX servers in each site, especially in the production site.

Thanks,