diff --git a/modules/monitoring.nix b/modules/monitoring.nix
index 0a9f12f..e9212fc 100644
--- a/modules/monitoring.nix
+++ b/modules/monitoring.nix
@@ -176,6 +176,91 @@
       "d /var/lib/node_exporter/textfile 0755 root root -"
     ];
 
+    # Custom textfile collectors: SAS SMART + ZFS pool health.
+    # node-exporter only parses SATA/NVMe SMART; SAS-specific predictive
+    # failure metrics (grown defects, non-medium errors, pending defects,
+    # ECC error counts) are not included by default and must be parsed
+    # manually from `smartctl -a` SAS output. ZFS pool health enum is
+    # also not exposed by the zfs collector (it gives ARC + pool I/O only).
+    systemd.services.skyw-textfile-collectors = lib.mkIf cfg.nodeExporter.enable {
+      description = "Write SAS SMART + zpool health textfile metrics";
+      serviceConfig = {
+        Type = "oneshot";
+        ExecStart = pkgs.writeShellScript "skyw-textfile-collectors" ''
+          set -u
+          OUT_DIR=/var/lib/node_exporter/textfile
+          TMP_SAS=$(mktemp "$OUT_DIR/sas_smart.prom.XXXXXX")
+          TMP_ZFS=$(mktemp "$OUT_DIR/zpool_health.prom.XXXXXX")
+
+          # SAS SMART
+          {
+            echo "# HELP smart_sas_power_on_hours Drive power-on hours"
+            echo "# TYPE smart_sas_power_on_hours counter"
+            echo "# HELP smart_sas_grown_defects Reallocated/grown defects"
+            echo "# TYPE smart_sas_grown_defects gauge"
+            echo "# HELP smart_sas_non_medium_errors SAS non-medium error count"
+            echo "# TYPE smart_sas_non_medium_errors counter"
+            echo "# HELP smart_sas_pending_defects Pending defects (predictive)"
+            echo "# TYPE smart_sas_pending_defects gauge"
+            echo "# HELP smart_sas_read_uncorrected Uncorrected read errors"
+            echo "# TYPE smart_sas_read_uncorrected counter"
+            echo "# HELP smart_sas_write_uncorrected Uncorrected write errors"
+            echo "# TYPE smart_sas_write_uncorrected counter"
+            for dev in /dev/sd?; do
+              [ -b "$dev" ] || continue
+              out=$(/run/wrappers/bin/sudo ${pkgs.smartmontools}/bin/smartctl -a "$dev" 2>/dev/null) || continue
+              echo "$out" | ${pkgs.gnugrep}/bin/grep -q "Transport protocol:.*SAS" || continue
+              name=$(basename "$dev")
+              poh=$(echo "$out" | ${pkgs.gnugrep}/bin/grep "Accumulated power on time" | ${pkgs.gawk}/bin/awk '{print $6}' | ${pkgs.coreutils}/bin/cut -d: -f1)
+              [ -z "''${poh:-}" ] && poh=$(echo "$out" | ${pkgs.gnugrep}/bin/grep "number of hours powered up" | ${pkgs.gawk}/bin/awk -F= '{gsub(/ /,"",$2); print $2}' | ${pkgs.coreutils}/bin/cut -d. -f1)
+              gd=$(echo "$out" | ${pkgs.gnugrep}/bin/grep "Elements in grown defect list" | ${pkgs.gawk}/bin/awk -F: '{gsub(/ /,"",$2); print $2}')
+              [ -z "''${gd:-}" ] && gd=$(echo "$out" | ${pkgs.gnugrep}/bin/grep "Grown defects during certification" | ${pkgs.gawk}/bin/awk -F= '{gsub(/ /,"",$2); print $2}')
+              nm=$(echo "$out" | ${pkgs.gnugrep}/bin/grep "Non-medium error count" | ${pkgs.gawk}/bin/awk -F: '{gsub(/ /,"",$2); print $2}')
+              pd=$(echo "$out" | ${pkgs.gnugrep}/bin/grep "Pending defect count" | ${pkgs.gnused}/bin/sed 's/.*count:\([0-9]*\).*/\1/')
+              ru=$(echo "$out" | ${pkgs.gnugrep}/bin/grep -A1 "^read:" | ${pkgs.coreutils}/bin/head -1 | ${pkgs.gawk}/bin/awk '{print $NF}')
+              wu=$(echo "$out" | ${pkgs.gnugrep}/bin/grep -A1 "^write:" | ${pkgs.coreutils}/bin/head -1 | ${pkgs.gawk}/bin/awk '{print $NF}')
+              [ -n "''${poh:-}" ] && echo "smart_sas_power_on_hours{device=\"$name\"} $poh"
+              [ -n "''${gd:-}" ] && echo "smart_sas_grown_defects{device=\"$name\"} $gd"
+              [ -n "''${nm:-}" ] && echo "smart_sas_non_medium_errors{device=\"$name\"} $nm"
+              [ -n "''${pd:-}" ] && echo "smart_sas_pending_defects{device=\"$name\"} $pd"
+              [ -n "''${ru:-}" ] && echo "smart_sas_read_uncorrected{device=\"$name\"} $ru"
+              [ -n "''${wu:-}" ] && echo "smart_sas_write_uncorrected{device=\"$name\"} $wu"
+            done
+          } > "$TMP_SAS"
+          chmod 0644 "$TMP_SAS"
+          mv -f "$TMP_SAS" "$OUT_DIR/sas_smart.prom"
+
+          # ZFS pool health
+          {
+            echo "# HELP zpool_health Pool health (0=ONLINE 1=DEGRADED 2=FAULTED 3=OFFLINE 4=UNAVAIL 5=REMOVED)"
+            echo "# TYPE zpool_health gauge"
+            ${pkgs.zfs}/bin/zpool list -H -o name,health 2>/dev/null | while read -r pool health; do
+              case "$health" in
+                ONLINE)   v=0 ;;
+                DEGRADED) v=1 ;;
+                FAULTED)  v=2 ;;
+                OFFLINE)  v=3 ;;
+                UNAVAIL)  v=4 ;;
+                REMOVED)  v=5 ;;
+                *)        v=6 ;;
+              esac
+              echo "zpool_health{pool=\"$pool\",state=\"$health\"} $v"
+            done
+          } > "$TMP_ZFS"
+          chmod 0644 "$TMP_ZFS"
+          mv -f "$TMP_ZFS" "$OUT_DIR/zpool_health.prom"
+        '';
+      };
+    };
+
+    systemd.timers.skyw-textfile-collectors = lib.mkIf cfg.nodeExporter.enable {
+      wantedBy = [ "timers.target" ];
+      timerConfig = {
+        OnBootSec = "30s";
+        OnUnitActiveSec = "5min";
+      };
+    };
+
     networking.firewall.allowedTCPPorts = lib.mkIf cfg.nodeExporter.enable
       [ cfg.nodeExporter.port ];
   };