monitoring: retain Pi fallback for VictoriaMetrics

services/monitoring/helmrelease.yaml

@@ -108,13 +108,6 @@ spec:
                     operator: In
                     values:
                       - "true"
-                  # VictoriaMetrics is too memory- and CPU-heavy for the Pi 4
-                  # workers. A hard Pi 5 requirement also moves old placements
-                  # instead of leaving them on a previously selected Pi 4.
-                  - key: hardware
-                    operator: In
-                    values:
-                      - rpi5
                   - key: kubernetes.io/hostname
                     operator: NotIn
                     values:
@@ -122,11 +115,27 @@ spec:
                       # attachment hosts and can surface volume I/O errors.
                       - titan-14
                       - titan-18
+                      # Keep the metrics database off this saturated Pi 4.
+                      - titan-12
                       - titan-20
                       - titan-21
                       - titan-22
                       - titan-24
           preferredDuringSchedulingIgnoredDuringExecution:
+            - weight: 100
+              preference:
+                matchExpressions:
+                  - key: hardware
+                    operator: In
+                    values:
+                      - rpi5
+            - weight: 50
+              preference:
+                matchExpressions:
+                  - key: hardware
+                    operator: In
+                    values:
+                      - rpi4
             - weight: 25
               preference:
                 matchExpressions: