AzCopy Upload Maxes Out Connection
BTW, in AzCopy v10, there's a parameter that lets you directly specify a cap on the amount of bandwidth it uses. E.g. --cap-mbps 200 will limit it to a max of 200 Mbps.
You can try reducing the number of concurrent operations:
/NC:"number-of-concurrent-operations"
Specifies the number of concurrent operations. AzCopy by default starts a certain number of concurrent operations to increase the data transfer throughput. Note that large number of concurrent operations in a low-bandwidth environment may overwhelm the network connection and prevent the operations from fully completing. Throttle concurrent operations based on actual available network bandwidth. The upper limit for concurrent operations is 512.
Applicable to: Blobs, Files, Tables
https://docs.microsoft.com/en-us/azure/storage/common/storage-use-azcopy#azcopy-parameters