Arq can restrict the rate at which it transfers data to S3. To set the restriction, open "Preferences" (from the "Arq" menu) and select the "Network" tab.
If you select this option, Arq uploads data to S3 at maximum speed unless you are using the network interactively. For example, if you're browsing a web site or watching a video, Arq detects this activity and slows its upload rate.
If you select this option, Arq will not exceed the kilobytes/second you specify when uploading data to S3.