Controller<=====Longest Part of cable===>Drive2<===Short bit===>Drive1
If I remember my cable theory correctly, all cables should be terminated in their characteristic impedance at both ends. If not, then reflections occur.
The higher the frequency, the greater effect they have on reliable use of the cable. As you said, cable length is also a factor.
Isn't this what "Time Domain Reflectromitry(SP?)" is based on?