I am copying files from USB external storage to my new synology NAS. It seems to be slow on occasions. Sometimes I average 130mbytes/sec other times average 10mbytes, occasionally it drops to "0", fortunately, not often.
Most of the big files are ISOs, many are MP4 and the rest a scattering of ZIPs, There are a huge number of smaller files and that is when I occasionally see "0" transfer rate for a second or two. I turned off "Real Time Scanning" but it didn't make a noticeable difference.
I read where the latest McAfee (which I have) only scan network files if "actionable'. Not sure what that means. Maybe it can be explained. I do a copy and paste from local USB3 external drives to the synology NAS. I would rather not scan the ISOs or MP4s as there are about 20TB of them.