So, since ATLAS Data Management on this case happens over FTS (even though the vast majority of the transfers are internal to a site), we turned up the number of slots for STAR-GLASGOW a bit, from 20 (our default) to 50 (which was fun) up to 80 (although we peaked at around 65 used).
With effectively no limit from FTS, our data rates were... impressive. Although it's an unfair comparison (everyone else was limited by FTS, and we were mostly moving things over the internal network), we managed to hit a peak transfer rate of 1.5GB/s internally (yes, that's 12Gbit/s), and sustain at around 8Gbits/s. That equated to around 2/3s of the total UK data movement over STAR channels, or roughly 2/3s of ATLAS's total traffic in this migration. At that rate, none of our disk servers were stressed, and the network switches were intensely relaxed.
Some exciting graphs follow:
