diff --git a/modules/spin-down.nix b/modules/spin-down.nix
index 748f42d..bce8b9f 100644
--- a/modules/spin-down.nix
+++ b/modules/spin-down.nix
@@ -19,13 +19,16 @@
 #   sudo hdparm -C /dev/disk/by-id/ata-WDC_WD40EFRX-68N32N0_WD-WCC7K0CPF0N1
 #   #=> drive state is: active/idle
 #
-# Spin down after 2 minutes (120s/5 = 24):
+# Spin down after 2 minutes (120s/5s = 24).
+# TODO: Western Digital (WD) Red/Green drives don't work properly. For low `-S` values, they spin down after **10** minutes. And for high values they don't spin down at all.
+# - https://superuser.com/questions/1746074/spin-down-not-working-on-wd-red
+# - https://askubuntu.com/questions/196473/setting-sata-hdd-spindown-time-for-western-digital-green-drives
+#
 #   sudo hdparm -S 24 /dev/disk/by-id/ata-WDC_WD40EFRX-68N32N0_WD-WCC7K0CPF0N1 # 4tb1
 #   sudo hdparm -S 24 /dev/disk/by-id/ata-WDC_WD30EFRX-68EUZN0_WD-WCC4N1173157 # 3tb1
 #   sudo hdparm -S 24 /dev/disk/by-id/ata-WDC_WD30EFRX-68EUZN0_WD-WMC4N0564095 # 3tb2
-#   #=> setting standby to 24 (2 minutes)
 #
-# ... after >> 2 minutes ...
+# ... after > 10 minutes ...
 #
 # Query disk without waking it up:
 #   https://wiki.archlinux.org/title/hdparm#Querying_the_status_of_the_disk_without_waking_it_up
@@ -50,8 +53,8 @@
 # https://www.reddit.com/r/NixOS/comments/751i5t/comment/do3f3l7/
 #   # Options:
 #   # -a <disk>: Select disk for subsequent parameters.
-#   # -i 180: Spin down after 2 minutes (180 seconds) of inactivity.
-#   ExecStart = "${pkgs.hd-idle}/bin/hd-idle -a /dev/disk/by-id/XXX-XXX-XXX -i 180";
+#   # -i 120: Spin down after 2 minutes (120 seconds) of inactivity.
+#   ExecStart = "${pkgs.hd-idle}/bin/hd-idle -a /dev/disk/by-id/XXX-XXX-XXX -i 120";
 
 {
   environment.systemPackages = with pkgs; [