I mounted a http direct url, which points to a rar file, to decompress it without downloading. I measured the read speed with utility "pv", which in fact is a filter and shows a progress indicator:
cat file.rar| pv |cat > file_copy.rar
Initial read speed is the usual 10 MB / sec, but always after reading 100 MB of data the read speed suddenly decreases to a few KB / sec.
Error log generated by option "-o debug": http://pastebin.com/W3Z6TMrY