postgres: avoid unstable nodes

infrastructure/postgres/statefulset.yaml

@@ -25,6 +25,7 @@ spec:
       serviceAccountName: postgres-vault
       nodeSelector:
         node-role.kubernetes.io/worker: "true"
+        hardware: rpi5
       affinity:
         nodeAffinity:
           requiredDuringSchedulingIgnoredDuringExecution:
@@ -35,7 +36,17 @@ spec:
                     values: ["true"]
                   - key: hardware
                     operator: In
-                    values: ["rpi4", "rpi5"]
+                    values: ["rpi5"]
+                  - key: kubernetes.io/hostname
+                    operator: NotIn
+                    values: ["titan-06"]
+          preferredDuringSchedulingIgnoredDuringExecution:
+            - weight: 100
+              preference:
+                matchExpressions:
+                  - key: kubernetes.io/hostname
+                    operator: In
+                    values: ["titan-05", "titan-07", "titan-08", "titan-11"]
       containers:
         - name: postgres
           image: postgres:15