Table of content
- Environmental Configuration
- Exchange Environment Configuration
- Mailbox Database Copy Configuration
- Exchange Data Configuration
- Exchange I/O Configuration
- Site Resiliency Configuration
- Lagged Database Copy Configuration
- Database Configuration
- Transport Configuration
- Where to Go from Here
Environmental configuration centers around the database configuration and is organized into eight sections:
|Exchange Environment Configuration — see page 3.||Site Resilience Configuration — see page 6.|
|Mailbox Database Copy Configuration — see page 5.||Lagged Database Copy Configuration — see page 8.|
|Exchange Data Configuration — see page 6.||Database Configuration — see page 10.|
|Exchange I/O Configuration — see page 6.||Transport Configuration — see page 10.|
Exchange Environment Configuration
In this section, you enter high-level environment configuration information. Inputs in this section consist of the following information:
- User profiles
- Whether the servers are physical or virtual
- Whether the site supports high availability (HA) and site resiliency
- Network connectivity between Active Directory sites
- Backup methodology
Mailbox Database Copy Configuration
This section allows you to enter the number of HA copies in the database availability group (DAG), including the primary and secondary datacenters and the lagged database copies. Best practice recommend that you have at least three copies of the database, including the active copy. Use a Lagged database copy if required.
Figure 2. Mailbox Database Copy Configuration
Exchange Data Configuration
This section considers overhead and compression factors. Generally, you can accept all default values to accommodate unexpected growth of the database. For capacity planning and to accommodate growth, however, it is good practice to set Data Overhead Factor to 20%.
Exchange I/O Configuration
This section specifies the input/output (I/O or read/write) overhead factor. We recommend that you accept the I/O Overhead Factor default value of 20%. If necessary, specify an Additional I/O Requirement for various applications.
Site Resiliency Configuration
In this section, you enter site-resiliency information for when the DAG is distributed across two datacenters.
Microsoft Exchange supports two site-resiliency user-distribution models: active/active and active/passive.
- Active/active — active databases mounted at both primary and secondary datacenters provide concurrent access to active users at both datacenters. If one datacenter fails, the database at the other datacenter is used by all active users.
- Active/passive — active database is mounted at the primary datacenter only, with passive copy hosted at a secondary datacenter. If the primary datacenter fails, the passive copy in the secondary datacenter is activated.
File Share Witness
As mailbox servers are added to the DAG, they are joined to the cluster and added to the list of voting members. For majority decisions to be reached, an odd number of quorum voters must be maintained. If there is an even number of mailbox servers, the DAG uses an external File Share Witness server to act as a tiebreaker.
The File Share Witness also plays a key role in protecting DAG from a total failure. If the DAG is distributed across two datacenters, place the File Share Witness on the datacenter that has the majority of users. If the secondary datacenter fails, the primary datacenter activates automatically, since the file share witness acts as the additional vote in primary datacenter. However, if the secondary datacenter needs to be activated manually then the File Share Witness may not be available.
To avoid this situation, Microsoft recommends you keep the File Share Witness at a third datacenter, which has reliable network connectivity to both the primary and secondary datacenters. This configuration allows the DAG to failover to an available datacenter automatically whenever any datacenter failover occurs and ensures that the File Share Witness is available to maintain the DAG cluster quorum.
Lagged Database Copy Configuration
Exchange Server includes features for the lagged database that obviates the need for requiring a dedicated server to host the lagged database copy. Now the host lagged database copy can be placed with other database copies on the server. Having a dedicated lag server keeps the configuration simple, but under-utilizes the server hosting the lagged database.
The following table describes the key parameters. The Exchange lagged database copy also offers self-protection features called “loose truncation” to free space on the disk if disk space gets low.
|Lagged Copy Log Replay Delay (Hours)||Forces stored Exchange information to wait before replaying the transaction logs on the target database.
|Lagged Copy Log Truncation Delay (Hours)||Forces the Microsoft Exchange replication service to wait before truncating log files that have been replayed into
the target database. The maximum time allowed for this configuration is 14 days, but recommended configuration is 0 hours.
The database configuration is used to determine the database sizes and the unique number of databases in the DAG. Initially, accept all default values. You can change the number of databases when you start tuning the database design.
Transport configuration is the final step under the Environment Configuration. The default settings as outlined thin the table below are usually acceptable.
|Message Queue Expiration (Days)||Number of days a message can reside in the transport queue after retrying multiple times before the message expires.||2|
|Safety Net feature (Days)||Keeps the redundant copy of the e-mail that was delivered to the target mailbox.||7|
Where to Go from Here
After entering the environmental configuration, proceed to part 2 of the series, which describes how to configure mailbox, backup, storage, processor, log replication, and environmental settings.