Assuming they are ideal diodes with a Vd of 0.7:
D1 will be forward biased so Vr1 is 4.301V
D2 will not be forward biased, so no current will flow since V-dV - 4.301 = 0,698; which is not enough to forward bias your ideal diode.
If the diodes where real, Vd would not be exactly 0.7 and the I-V relation would not be a vertical straight line, it would be a non-linear funcion with a slope affected by temperature and other factors. Wikipedia article "Shockley diode equation" covers it. Also noise in the power supplies should be taken into account. Summarizing, a lot more to take care of.