To improve performance, use multiple access nodes, streams, and service accounts. You can also use the storage accelerator. For security, use encryption.
To overcome the effects of throttling and to improve performance during backups, use multiple mailbox access nodes, streams, and service accounts or Azure apps. Exchange Online follows the forever incremental model.
Example: Backup Operation
1 access node, 10 streams, 5 service accounts (Basic Authentication) or 5 Azure apps (Modern Authentication)
2 access node, 20 streams, 20 service accounts (Basic Authentication) or 10 Azure apps (Modern Authentication)
Example: Backup and Cleanup Operation
1 access node, 10 streams, 10 service accounts (Basic Authentication) or 10 Azure Apps (Modern Authentication)
2 access node, 20 streams, 20 service accounts (Basic Authentication) or 10 Azure Apps (Modern Authentication)
A license is not required for an Exchange Online service account. You must convert the user mailbox to a shared mailbox and remove the Office 365 license for the Exchange Online service account.
You can accelerate backups to cloud storage libraries by installing the storage accelerator on all mailbox access nodes. For more information, see Accelerating Cloud Storage Backups from Clients.
When an Exchange Online app is configured to back up data to a cloud storage library, data is routed through the MediaAgent that is configured in the subclient that the backup was started from. Thus, the data is sent to the MediaAgent first, and then it is sent from the MediaAgent to the cloud storage library. To make backups faster, you can can configure the app to send the data directly to the cloud storage library.
You can add mailbox access nodes, MediaAgents, Index Servers, and Web Servers in Azure or on-premises, without impacting backup performance.
You can monitor CPU and memory resources on the Exchange Online access nodes and the Index Server using any monitoring tool, or you can configure system monitoring. For more information, see System Monitoring.
You can use the CVOfficeBandwidthMonitor tool to overcome backup performance issues.
You can configure encryption on an Exchange Online app to protect data during backups and restores.