Did futher diagnostic work - the sending rate had an approx. average of 40 MB/sec and the principal sent 37 GB to the mirror node in 15 min.
The restore rate was not nearly as efficient. The restore rate was quite slow - most times the restore rate was < 5 MB/sec but on individual occassions, the restore rate jumped to 36 MB/sec.
Any idea why the restore rate was so slow? FYI - the underlying subsystem is FusionIO, so writes should be fast.