A few tips to get better speeds at rendering on multi GPU systems with Redshift 3D & Maxon’s Cinema4D.
1.
If a CPU is busy loading and unloading the scene to and from multiple GPUs and still rendering at the same time it can be to much of a burden. If such is the case try using only GPUs to render. To do this just uncheck the box to use CPUs for rendering in Redhsift’s settings. Let the CPU handle every processes but rendering and check the results.
2.
You might try opening a few instances of C4D and have maximum of 2 GPUs active on each instance. This can give good results with scenes where a single frame renders under a few minutes.
3.
If using render managers try having 1 GPU active per C4D instance and minimum 1-2 CPU cores assigned to each C4D instance. This solution however consumes lots of memory, easily far beyond accessible amount of RAM. Setting a large enough paging file on a fast nvme or ssd drive is a necessity. Works best with scenes where each frame renders in a few minutes on one GPU
Have fun and hope this helps!