Spin down the HDDs when not in use

configuration.nix

@@ -97,6 +97,10 @@
   services.journald.extraConfig = "SystemMaxFiles=7";
 
   # Import other configuration modules
-  imports = [ ./modules/hardware-configuration.nix ./modules/networking.nix ];
+  imports = [
+    ./modules/hardware-configuration.nix
+    ./modules/networking.nix
+    ./modules/periodic.nix
+  ];
 
 }

modules/periodic.nix

@@ -0,0 +1,13 @@
+{ config, lib, pkgs, ... }:
+
+{
+  # Idle HDDs when not used
+  systemd.services.hd-idle = {
+    description = "Idle HDDs when not in use";
+    wantedBy = [ "default.target" ];
+    path = with pkgs; [ hd-idle ];
+    script = "${pkgs.hd-idle}/bin/hd-idle";
+    serviceConfig.Type = "simple";
+    after = [ "shield-unit.mount" ];
+  };
+}