Rowing for cardio

[rivermetimbers]

Today I decided to try out the rowing machine for the second time in my life. I usually run 3 times a week, about 2 miles, as my cardio that goes along with my lifting. Anyway, I decided to do 1000 meters at a high resistance (8/10) and then after a little break did 700 meters at medium resistance (5/10). Anyway, i felt like it provided me with a good cardio workout and just wanted to know if it actually would be pretty beneficial to add it to my workout, maybe 2 times per week. If so, at what resistance should I be doing and what distance in order to actual benefit from it? Thanks