From the course: Deploying Exchange Server 2019

Plan for Exchange clustering - Microsoft Exchange Server Tutorial

From the course: Deploying Exchange Server 2019

Start my 1-month free trial

Plan for Exchange clustering

“

- [Instructor] A Database Availability Group or a DAG is a group of Exchange servers connected using the same version of software and operating systems. One of the requirements is going to be that hardware has the same amount of network adapters on both servers. And they'll also need to be the same speed adapters as well. If one side is using gigabit adapters, the other side needs to do that as well. There is no direct routing that allows heartbeat traffic from the replication network on one DAG member server to the MAPI network on another DAG member server. And two subnets are going to be required. The first is for the DAG replication, and the second is for the MAPI connectivity. You can accomplish this in a couple of different ways. One is by supplying two IP addresses on a single network card, or two network cards each on a different subnet. Regardless of their geographic location relative to other DAG members, each member of the DAG must have round trip network latency no greater than 500 milliseconds between each other member. And DAG networks support Internet Protocol IP version four and IP version six. We'll also need a way to break a tie, a tie that says one server is down and the other server's in charge. So that's going to require a witness server. A witness server is a server outside of DAG that's used to achieve and maintain quorum when the DAG has an even number of members. DAGs with an odd number of members don't need a witness server. The witness server is also available to solve the split-brain syndrome, and that's a condition that occurs when DAG members can't communicate with each other but are still running. Split brain syndrome is prevented by always requiring a majority of the DAG members to be available and interacting for the DAG to be operational. We're also going to need a public SAN certificate. And SAN stands for Subject Alternative Name. We demonstrated this in a previous video when we purchased a SAN certificate and then installed it on our Exchange server. The certificate needs to be installed on both of the DAG members if there's two in a DAG. And if there's additional members, it needs to be installed on those as well. And that's because the DAGs need to respond to the users using the same certificate and the same host names. A DNS server with host records for each server is also going to be required. What many people may not realize is that if you are inside a network and you have a DNS server, you need to point the IP address to the inside IP address of the Exchange server you have onsite. If you're outside of the network, you'll need to use a public DNS server that points to the public IP address that's then translated through the firewall using network address translation to the private IP address. And that private IP address links to one of the DAG members. By setting up a high availability deployment, an organization can recover from a server failure without downtime from connecting to the Exchange server.

Contents