I’ve tried using Robocopy bandwidth throttling switch many times in the past but never seemed to figure it out. Today I have the need to start a slow copy for many files over a T1 line and went in search of the solution again. I came across this blog post that gave a formula that works perfectly.
D = (Ba-Bd) / (Ba*Bd) * 512 * 1000
Where D = the /IPG switch value you will enter in Robocopy.
Ba = the available bandwidth of the link in Kbps.
Bd = the desired bandwidth you want to consume in Kbps.
In my case the link is a T1 so I used 1500 for Ba and I wanted to use 200Kbps. So I ended up with 2218 for the IPG switch and now it’s a nice slow copy that will go overnight.