Exchange Server/Plan and designing

From ITHandbook

Overview

By configuring high availability, you can protect server databases to prevent data loss and implement failover in the event of an outage.

You should identify the requirements for the deployment during the planning phase.

General Prerequisites

  • Two or more servers must be running the same version of the OS and the Exchange Server.
  • Sufficient storage to store the mailbox databases.
  • Fast network connection for database-level failover actions.
  • Domain Name System (DNS) or Load-Balancer for network load balance.

High availability implementation

Minimal high availability implementation

The minimal high availability implementation only requires the deployment of additional servers.

Set the URLs of both servers to be the same and configure round-robin DNS to implement network load balancing. For more information, refer to Configure URL in Exchange.

Implement database high availability by configuring Database Availability Group (DAG). For more information, refer to Database Availability Group (DAG).

  • Advantages
    • Can save costs.
    • Easy to configure.
  • Disadvantages
    • For external access, two or more public IP addresses are required.
    • Cannot fine-grained control over traffic distribution.
    • No dedicated replication network for database-level failover.

Common high availability implementation

Implement high availability by deploying a load balancer.

  • Advantages
    • Can fine-grained control over traffic distribution by using a load balancer.
    • Commonly used implementation solutions.
  • Disadvantages
    • Require to purchase a license (For software load balancer) or equipment (For hardware load balancer). This leads to increased costs.
    • You need additional knowledge to configure the load balancing infrastructure.
    • No dedicated replication network for database-level failover.

Another high availability implementation

Each server has two network adapters for Database Availability Groups (DAGs).

One for the MAPI network for mail communication, and the other for the replication network.

  • Advantages
    • Can fine-grained control over traffic distribution by using a load balancer.
    • Dedicated replication network between servers to achieve database-level failover.
  • Disadvantages
    • Require to purchase a license (for software load balancer) or equipment (for hardware load balancer). This leads to increased costs.
    • You need additional knowledge to configure the load balancing infrastructure.
    • If outbound traffic goes out through a single WAN link (as the picture shows), it makes no sense to configure the replication network.
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