JKoelker -
Try using 'snapmirror status -l'.
You can see the duration and transfer size for the last transfer:
Last Transfer Size: 1120000 KB
Last Transfer Duration: 00:03:47
Do the math to divide the transfer size by the number of seconds in the duration.
You can also get this information from the snapmirror logs.
I hope this response has been helpful to you.
At your service,
Eugene E. Kashpureff, Sr.
Independent NetApp Consultant http://www.linkedin.com/in/eugenekashpureff
Senior NetApp Instructor, IT Learning Solutions http://sg.itls.asia/netapp
(P.S. I appreciate 'kudos' on any helpful posts.)