A Microsoft file hosting and synchronization service.
I think it's interesting that there are so many forums posts about this topic, and, every time it seems that a Microsoft support agent chimes in with all these tips for the end user to try to improve performance, seemingly implying (or outright saying) that the issue is not Microsoft but rather that customer.
Let's be very clear here, the issue is Microsoft and it is throttling. Not only that, but Microsoft very clearly says that they throttle OneDrive and Sharepoint. Hopefully this helps folks at least in understanding what the issue is and stops people from needlessly troubleshooting their own setup ad infinitum.
Here are a couple Microsoft published resources on the topic. Note, these pages largely refer to Sharepoint (or Sharepoint Online) but make no mistake that this encompasses the OneDrive service as well (as OneDrive and Sharepoint are largely the same and are overlapping in feature and function).
https://learn.microsoft.com/en-us/sharepointmigration/sharepoint-online-and-onedrive-migration-speed https://learn.microsoft.com/en-us/sharepoint/dev/general-development/how-to-avoid-getting-throttled-or-blocked-in-sharepoint-online
Of particular note, a few key pieces you may want to take away from these published pages:
- We have implemented tighter throttling limits on background apps (migration, DLP and backup solutions) during weekday daytime hours. You should expect that these apps will achieve very limited throughput during these times. However, during evening and weekend hours for the region, the service will be ready to process a significantly higher volume of requests from background apps.
- Can Microsoft turn off the throttle to help me with migration? No. Throttling is in place to protect the reliability and availability of the service. Throttling rules cannot be disabled or suspended.
I can confirm from considerable experience doing many company migrations and integrations that the throttling eases during evening and weekend hours.