@florent Thanks for your reply! We have started to migrate thousands of VMs, so disk transfer speed is important for us.. We will also do our detailed tests soon with different threads setting and publish it here. I think threads=1 is a good and logical default, but not efficient. Others might complain if you set it to a higher value. Configuration option would be a real good solution.

@Aimdev eh man people use a lot of different browsers and don't always remember all the options, the dev's here are top 5 star really. I did it because I do use Safari and simply replicated the steps and noticed the pop-up warning (I never allow pop-ups by default) so I figured that could be the issue. Have a great weekend you too and you're welcome!