I am doing something similar, and seeing speeds of about 2MB/sec.
However, I can confirm that it is still using server side copy because the verbose output says so.
2020-01-03 19:26:05 INFO : Files/files/project1.txt: Copied (server side copy)
The directory I'm moving contains about 400 small text files, sized between a few k and 2MB. So I think the slow speeds are not the transfer itself, but rather the overall throughput due to latency grabbing the files from storage.
The throughput rclone shows with -P is actually an average. So, if my files are transferring at 100MB/sec, but between every file there is a pause of a few seconds, rclone would show the kind of numbers I'm witnessing at the moment.
Another way to see what I'm talking about is to run with -P
Transferred: 5.326G / 5.624 GBytes, 95%, 2.791 MBytes/s, ETA 1m16s
Checks: 0 / 0, -
Transferred: 307 / 614, 50%
Elapsed time: 4m50.2s
- Files/files/project1.txt: 0% /138.062k, 0/s, -
- Files/files/project2.txt: 0% /216.468k, 0/s, -
- Files/files/project3.txt: 0% /671.354k, 0/s, -
- Files/files/project4.txt: 0% /160.347k, 0/s, -
NOTE: math won't work because this isn't the full output
The files being transferred always show 0% and 0/s because they transfer almost instantly, and are replaced by the path to the next file, which also shows 0% until it is replaced by the path to the next file, rinse repeat.
Might that explain what you're experiencing?