By default, Azure File Sync will utilize as much bandwidth as it needs to complete its sync tasks. If you have to sync a lot of large files, this could cause a strain on your network. Unfortunately there’s no way to limit Azure File Sync bandwidth through the Azure portal, instead you have to use Powershell on the server that’s running the Azure Storage Sync Agent.
How to Limit Azure File Sync Bandwidth via Powershell
Log into the server where Azure Storage Sync Agent is running