diff --git a/src/disk.sh b/src/disk.sh
index ccf3e89..492c610 100644
--- a/src/disk.sh
+++ b/src/disk.sh
@@ -573,18 +573,25 @@ addDevice () {
   [ ! -b "$DISK_DEV" ] && error "Device $DISK_DEV cannot be found! Please add it to the 'devices' section of your compose file." && exit 55
 
   local sectors=""
-  local result logical physical
-  result=$(fdisk -l "$DISK_DEV" | grep -m 1 -o "(logical/physical): .*" | cut -c 21-)
-  logical="${result%% *}"
-  physical=$(echo "$result" | grep -m 1 -o "/ .*" | cut -c 3-)
-  physical="${physical%% *}"
+  local dev_type=""
+  dev_type=$(lsblk -no TYPE "$DISK_DEV" 2>/dev/null | head -n1)
 
- if [ -n "$physical" ]; then
-    if [[ "$physical" != "512" ]]; then
-      sectors=",logical_block_size=$logical,physical_block_size=$physical"
+  # Only detect and apply sector sizes for partitions, not whole disks
+  # Whole disk passthrough with explicit sector sizes causes DSM not to recognize the disk
+  if [[ "$dev_type" == "part" ]]; then
+    local result logical physical
+    result=$(fdisk -l "$DISK_DEV" | grep -m 1 -o "(logical/physical): .*" | cut -c 21-)
+    logical="${result%% *}"
+    physical=$(echo "$result" | grep -m 1 -o "/ .*" | cut -c 3-)
+    physical="${physical%% *}"
+
+    if [ -n "$physical" ]; then
+      if [[ "$physical" != "512" ]]; then
+        sectors=",logical_block_size=$logical,physical_block_size=$physical"
+      fi
+    else
+      warn "Failed to determine the sector size for $DISK_DEV"
     fi
-  else
-    warn "Failed to determine the sector size for $DISK_DEV"
   fi
 
   DISK_OPTS+=$(createDevice "$DISK_DEV" "$DISK_TYPE" "$DISK_INDEX" "$DISK_ADDRESS" "raw" "$DISK_IO" "$DISK_CACHE" "" "$sectors")