Hi,
I made a ticket with backblaze and got this answer,
Hello,
This is due to the latency on the connection.
To upload more quickly you will want to get a software that supports multiple threads to upload the data.
That way you can use multi threads to bolster the upload output on the connection.The 3rd party applications that you can utilizes are here: Cloud Storage Options: B2 Partner Integrations
Not all integrations will have threading.Thanks,
xxxxxxxxxxThe Backblaze Team