In my AS6704T, I have two 16TB IronWolf Pros and two 1TB WD Red NVMes running in Raid 1 cache. The NVMe drives will get thermo warnings within 5 minutes if I don't at least have the fan running at 750 rpm. I think the links you sent should help me add the NVMe drives in without too much effort. I was using your script (with a few changes) before last week, but when I put the new AsustorPFD plugin on, I thought I'd give the Dynamix control a try. It works "OK" by setting the minimum PWM speed to keep the fan running at low speed, but it's not ideal. When the HDDs spin up it works OK, but I try to keep them spun down as much as possible. The 1TB cache setup does a nice job and keeping them off. Thanks for the links @Terebi I'll post when I get it done.