our $config_num_disks = 4; # number of warmest disks to use for average temperature
our $config_Ta = 40;       # target average temperature for X warmest disks
our $config_Kp = 8/3;
our $config_Ki = 0;
our $config_Kd = 30;
our $config_hd_fan_start = 36; # HD fan duty cycle when script starts