diff --git a/man/man5/vdev_id.conf.5 b/man/man5/vdev_id.conf.5
index 740808f6daa..aaf91825a6c 100644
--- a/man/man5/vdev_id.conf.5
+++ b/man/man5/vdev_id.conf.5
@@ -95,7 +95,7 @@ and a default mapping applied to the others.
 .It Sy zpad_slot Ar digits
 Pad slot numbers with zeros to make them
 .Ar digits
-long.
+long, which can help to make disk names a consistent length and easier to sort.
 .
 .It Sy multipath Sy yes Ns | Ns Sy no
 Specifies whether
diff --git a/udev/vdev_id b/udev/vdev_id
index 898710f6ea8..5897fea3ed6 100755
--- a/udev/vdev_id
+++ b/udev/vdev_id
@@ -432,6 +432,9 @@ sas_handler() {
 		SLOT=$(echo "$d" | sed -e 's/^.*://')
 		;;
 	"bay_lun")
+		# Like 'bay' but with the LUN number appened. Added for SAS 
+		# multi-actuator HDDs, where one physical drive has multiple
+		# LUNs, thus multiple logical drives share the same bay number
 		i=$((i + 2))
 		d=$(eval echo '$'{$i})
 		LUN="-lun$(echo "$d" | sed -e 's/^.*://')"