diff --git a/UPGRADE.md b/UPGRADE.md
new file mode 100644
index 0000000..e07727b
--- /dev/null
+++ b/UPGRADE.md
@@ -0,0 +1,40 @@
+# Upgrade Notes
+
+## 3.7.166
+
+### Parent database default volume size increased to 15Gi
+
+The default value of `parent.database.volumesize` has been increased from `5Gi` to `15Gi`.
+
+This change better reflects the storage requirements of a Netdata parent node across a wider range of real-world deployments.
+
+**Who is affected**
+
+Only users who rely on the default value — i.e., who have not explicitly set `parent.database.volumesize` in their own `values.yaml` or `--set` flags.
+
+**Potential upgrade failure**
+
+If your cluster's StorageClass does not have `allowVolumeExpansion: true`, `helm upgrade` will fail with an error similar to:
+
+```
+PersistentVolumeClaims "netdata-parent-database" is forbidden: only dynamically provisioned
+pvc can be resized and the storageclass that provisions the pvc must support resize
+```
+
+**How to avoid this**
+
+Pin the volume size to your current value to prevent any resize attempt:
+
+```yaml
+parent:
+  database:
+    volumesize: 5Gi
+```
+
+Or, if you want to expand but your StorageClass does not support automatic expansion, manually resize the PVC before running `helm upgrade`:
+
+```bash
+kubectl patch pvc netdata-parent-database -p '{"spec":{"resources":{"requests":{"storage":"15Gi"}}}}'
+```
+
+Note that manual resizing also requires the StorageClass to support volume expansion. On clusters where expansion is not supported at all, keep the old value pinned in your values.
diff --git a/charts/netdata/README.md b/charts/netdata/README.md
index 1313dba..f9fed67 100644
--- a/charts/netdata/README.md
+++ b/charts/netdata/README.md
@@ -943,7 +943,7 @@ true
 			<td>parent.database.volumesize</td>
 			<td>string</td>
 			<td><pre lang="json">
-"5Gi"
+"15Gi"
 </pre>
 </td>
 			<td>The storage space for the PVC of the parent database</td>
diff --git a/charts/netdata/values.yaml b/charts/netdata/values.yaml
index 8aedf66..0128291 100644
--- a/charts/netdata/values.yaml
+++ b/charts/netdata/values.yaml
@@ -345,7 +345,7 @@ parent:
     storageclass: "-"
     # -- The storage space for the PVC of the parent database
     # @section -- Parent
-    volumesize: 5Gi
+    volumesize: 15Gi
 
   alarms:
     # -- Whether the parent should use a persistent volume for the alarms log