A typical Exchange site replication copies the Windows environment (Active Directory, Domain Controller and so on) through the Wide Area Network (WAN) to another site. The Exchange Data on the storage system is copied to the other site using SnapMirror.
To recover from a total site outage in a minimum amount of time, you can replicate your Exchange Server environment to a remote site. Then, if the primary site is destroyed, you can re-create your Exchange environment on the site you copied.
The following diagram shows a typical Exchange site replication:

The Windows environment (Active Directory, Domain Controller, etc.) is replicated through the Wide Area Network (WAN) to the replicated site.
For more information about replicating your Windows environment and using a replicated environment to recover from a disaster, see your Windows documentation.
The Exchange data on the storage system is mirrored using SnapMirror to a storage system on the replicated site.
For more information about setting up SnapMirror, see your Data ONTAP System Administration Guide.