No one is suggesting that your Lenovo W520 isn't a "top of the line" machine. However, the recovery process under way is essentially a straightforward I/O operation and, unless I've misread the W520 specs
, at least one of the drives involved is external. Was that drive and its external connection included in those wonderful performance results you mention and under what Windows version were they obtained? What type of connection to what type of drive enclosure and what driver support is provided for it (if any) in your rescue media build based on what PE base version?
I understand that you are looking for a theory, but proper theories must be based on carefully observed and reported facts, not just any old wild speculation. Unless you are prepared to consider and respond to factors such as those listed in the relevant KB article
, it's going to be very difficult to help you to pin down the cause and resolve the problem. I can assure you of one thing. The results that you are seeing aren't just unusual and unacceptable but spectacularly so, and I can think of nothing attributable to the Reflect software alone that could possibly account for it. Nevertheless, if you believe that the problem is due to Reflect itself, you can prove or disprove the point quite simply by trying to copy a large file directly using the PE Explorer as suggested. If you get similar painfully slow results doing that, then the problem is not being caused by Reflect. It's either hardware-related or due to some supporting deficiency in the rescue media build.
You should at least try rebuilding your rescue media with the current Reflect version and with that external drive attached during the build process. And try using PE10 as the base if you used some earlier PE version previously as PE10 will support more and newer hardware natively.
Regards, Richard V. ("Arvy")