Fix inefficient DRIVE_MAP declaration pattern

Declare DRIVE_MAP as global at function start and populate directly,
instead of creating a local array and copying to global. Also added
proper variable quoting and function documentation.

Fixes: #1

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

driveAtlas.sh

@@ -243,28 +243,33 @@ get_storage_controllers() {
     done
 }
 
+#------------------------------------------------------------------------------
+# build_drive_map
+#
+# Builds a global associative array mapping physical bay numbers to device names.
+# Uses PCI paths from SERVER_MAPPINGS to resolve current device assignments.
+#
+# Sets: DRIVE_MAP (global associative array)
+#   Keys: Bay identifiers (1, 2, ..., m2-1, m2-2, etc.)
+#   Values: Device names (sda, nvme0n1, etc.)
+#------------------------------------------------------------------------------
 build_drive_map() {
-    local host=$(hostname)
-    declare -A drive_map
+    local host="$(hostname)"
+    local mapping="${SERVER_MAPPINGS[$host]}"
 
-    local mapping=${SERVER_MAPPINGS[$host]}
+    # Declare global array directly instead of copying from local
+    declare -g -A DRIVE_MAP=()
 
     if [[ -n "$mapping" ]]; then
         while read -r path slot; do
             [[ -z "$path" || -z "$slot" ]] && continue
 
             if [[ -L "/dev/disk/by-path/$path" ]]; then
-                local drive=$(readlink -f "/dev/disk/by-path/$path" | sed 's/.*\///')
-                drive_map[$slot]=$drive
+                local drive="$(readlink -f "/dev/disk/by-path/$path" | sed 's/.*\///')"
+                DRIVE_MAP[$slot]="$drive"
             fi
         done <<< "$mapping"
     fi
-
-    # Make drive_map available globally
-    declare -g -A DRIVE_MAP=()
-    for key in "${!drive_map[@]}"; do
-        DRIVE_MAP[$key]=${drive_map[$key]}
-    done
 }
 
 get_drive_smart_info() {