How to create a full SharePoint site backup (100K+ files, ~400GB) to another SharePoint site monthly?

Hi community,

We are looking to implement a monthly full-site backup solution for one of our SharePoint Online sites.

🔹 Current Site Info:

• Files: 100,000+

Total Data Size: ~400 GB

Structure: Includes folders, subfolders, and documents

Accessed frequently by teams

🔹 Backup Requirements:

We want to create a backup of the entire site into another dedicated SharePoint "Backup Site".

This backup should run automatically on the 1st of every month.

Before each new backup, the previous month's backup should be deleted from the backup site to avoid storage issues.

🔹 Question:

What is the best and most reliable way to automate this entire backup process considering:

The large number of files and folders

SharePoint/Power Automate limitations

Avoiding timeouts or throttling

We explored Power Automate, but it hits file limits and errors on large folder operations. Is there an alternate method or Microsoft-recommended approach/tool for full site replication or backup?

Any guidance or best practices will be highly appreciated.

Thanks in advance!