Hi, 429 is throttling, Microsoft are rate limiting the number of requests you can make at once. Either let it run and sort itself out or to avoid this use fewer threads, or additional auxiliary accounts (this works but is a deprecated feature because Microsoft don’t like tricks to bypass rate limiting, there’s also a tenant level rate limit that you’re possibly going to reach if you scale too far and impact your users working.

Auxiliary Accounts were used for organizations added with basic authentication or modern authentication with legacy protocols.

With organizations added with modern app-only authentication, we use Backup Applications.

As Michael told you, Microsoft doesn‘t like it when you use multiple Backup Applications. Our team has discussed this matter with Microsoft and together we came to a recommendation. Please see the following statement in our user guide:

https://helpcenter.veeam.com/docs/vbo365/guide/impact_on_performance.html?ver=70

Best,

Fabian

i just added the 5 Auxiliary backup applications, so thanks for tip :) 

Depending on how fast your platform is, 5 auxiliary backup applications could certainly hit your tenant level bottleneck. I’ve seen this in organisations with tens of thousands of E5 licenses, it’s a very real bottleneck.

I don’t know whether you’re deploying VB365 internally or providing this to a business on a consultancy basis, but I’d suggest setting expectations that this COULD impact user productivity. In which case you could reduce the number of auxiliary applications you’re using, or adjust the number of threads, or specify times in which the backup is/isn’t allowed to run. You’ll find this info in the link below:

https://helpcenter.veeam.com/docs/vbo365/guide/specify_scheduling_options.html?zoom_highlight=permitted+backup+window&ver=70#stp