Why are the disks not loaded at 100% at the same time?

Question

Windows

I create Chia rafts on 2 Disks. One Sata SSD drive, the second - NVMe connected via an adapter to PCI Express. If one disk is loaded at 100 percent, then the second automatically drops to 5-15 percent, and vice versa. It seems that they can only work in turns. What could be the problem and how can it be solved?

The percent is loaded by 60 percent on average. Tried to reduce the number of baskets from 128 to 64 - does not help. 5 rafts are plowing at the same time.

Answer 1

And on what iron? What generation of sata? What pci? x16?
I'll try to give an answer
H.z. what is a raft chia but
Since one sata ssd second pci nvme
The level of load distribution will not be uniform.
Due to different drive interfaces, the speed will be different. The rest is data.