3-2-1 Rule

The 3-2-1 rule is one of the basics when talking about data protection. This best practice tells you to have:

Three copies of the data
Stored on two different media
of which one should be off-site (and maybe also offline)

You should consider these rules also during your planning of the backup for Microsoft 365. Depending on the chosen storage architecture for your Veeam Backup for Microsoft 365 infrastructure, there are different strategies to meet the 3-2-1 design guideline.

Object Storage

When you’re using Object Storage as the backup target Veeam Backup for Microsoft 365 can create a Backup-Copy into a secondary Object Storage location based on Azure Blob Storage Archive access tier, Amazon S3 Glacier storage class, or Amazon S3 Glacier Deep Archive storage class.

Alternativly you can also use Object Storage native functionality for replicating the Object Storage Repository data with Object replication for block blobs. With this native replication, the entire repository is replicated and can be used for restores when the primary location is not available anymore. The process to mount the secondary location is just as simple as:

Remove the primary repository that is been replicated from the Repository configurations within Veeam Backup for Microsoft 365
Remove the Object Replication Policy for the storage container.
Reattach the repository replication storage container to the Veeam Backup for Microsoft 365 configuration with a new empty local cache folder and run the repository synchronization

Local Storage

When you’re using Local Storage as the backup target, Veeam Backup for Microsoft 365 can’t create a Backup-Copy directly. To meet the 3-2-1 design guideline, you’ve two possible options:

Create a secondary backup job to write the Backup data to another backup repository.
Use Veeam Backup and Replication to create a backup of the entire Veeam Backup for Microsoft 365 implementation. Veeam Backup and Replication has an application integration to ensure an application consistent backup and do single item restores directly with the Veeam Explorers. More information of this solution can be found on Protect VB365.

Resources

Backup-copy Helpcenter information – Helpcenter page with details on Backup Copy
Object replication for block blobs - Object replication for block blobs
Protect VB365 – Protecting Veeam Backup for Microsoft 365 with Veeam Backup and Replication