diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index a1a063f76..bd3630fdf 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -1276,6 +1276,10 @@ jobs:
             --set httpRoute.enabled=true \
             --set 'httpRoute.parentRefs[0].name=gateway' \
             > "$out/http-route.yaml"
+          helm template trek charts/trek \
+            --set 'persistence.data.accessModes[0]=ReadWriteMany' \
+            --set 'persistence.uploads.accessModes[0]=ReadWriteMany' \
+            > "$out/access-modes.yaml"
           helm template trek charts/trek \
             --set podSecurityContext.runAsUser=1000 \
             --set podSecurityContext.runAsGroup=1000 \
diff --git a/charts/README.md b/charts/README.md
index 2d7e8dc3e..62060538b 100644
--- a/charts/README.md
+++ b/charts/README.md
@@ -43,7 +43,8 @@ See `values.yaml` for more options.
 ## Notes
 - Ingress is off by default. Enable and configure hosts for your domain.
 - PVCs use the cluster's default StorageClass. Set `persistence.data.storageClassName` and/or `persistence.uploads.storageClassName` to bind a specific class.
-- To use your own PVCs, set `persistence.data.existingClaim` and/or `persistence.uploads.existingClaim`. The other values for that volume (size, storageClassName, annotations) are then ignored.
+- Both PVCs are `ReadWriteOnce`. Set `persistence.data.accessModes` and/or `persistence.uploads.accessModes` to override, for example `[ReadWriteMany]` so a backup pod can mount the volume. On the data volume such a pod may only read: SQLite corrupts `travel.db` when a second process writes it over a network filesystem.
+- To use your own PVCs, set `persistence.data.existingClaim` and/or `persistence.uploads.existingClaim`. The other values for that volume (size, storageClassName, accessModes, annotations) are then ignored.
 - With `persistence.enabled: false`, the data and uploads volumes use an `emptyDir` — storage is ephemeral and lost on pod restart. Intended for testing only.
 - `JWT_SECRET` is managed entirely by the server — auto-generated into the data PVC on first start and rotatable via the admin panel (Settings → Danger Zone). No Helm configuration needed.
 - `ENCRYPTION_KEY` encrypts stored secrets (API keys, MFA, SMTP, OIDC) at rest. Recommended: set via `secretEnv.ENCRYPTION_KEY` or `existingSecret`. If left empty, the server falls back automatically: existing installs use `data/.jwt_secret` (no action needed on upgrade); fresh installs auto-generate a key persisted to the data PVC.
diff --git a/charts/trek/templates/pvc.yaml b/charts/trek/templates/pvc.yaml
index 5e6872dea..149175081 100644
--- a/charts/trek/templates/pvc.yaml
+++ b/charts/trek/templates/pvc.yaml
@@ -11,7 +11,7 @@ metadata:
   {{- end }}
 spec:
   accessModes:
-    - ReadWriteOnce
+    {{- toYaml (.Values.persistence.data.accessModes | default (list "ReadWriteOnce")) | nindent 4 }}
   {{- with .Values.persistence.data.storageClassName }}
   storageClassName: {{ . | quote }}
   {{- end }}
@@ -33,7 +33,7 @@ metadata:
   {{- end }}
 spec:
   accessModes:
-    - ReadWriteOnce
+    {{- toYaml (.Values.persistence.uploads.accessModes | default (list "ReadWriteOnce")) | nindent 4 }}
   {{- with .Values.persistence.uploads.storageClassName }}
   storageClassName: {{ . | quote }}
   {{- end }}
diff --git a/charts/trek/values.yaml b/charts/trek/values.yaml
index c2a4a4c53..648058884 100644
--- a/charts/trek/values.yaml
+++ b/charts/trek/values.yaml
@@ -247,12 +247,21 @@ persistence:
     size: 1Gi
     # Leave empty to use the cluster's default StorageClass; set to bind a specific class.
     storageClassName: ""
-    # Bind an existing PVC. The other values (size, storageClassName, annotations) are then ignored.
+    # Access modes of the claim. ReadWriteMany lets another pod mount the volume, for
+    # example a backup sidecar, but only for reading: SQLite needs every writer on one
+    # host, so two pods writing travel.db over a network filesystem corrupt it.
+    accessModes:
+      - ReadWriteOnce
+    # Bind an existing PVC. The other values (size, storageClassName, accessModes,
+    # annotations) are then ignored.
     existingClaim: ""
     annotations: {}
   uploads:
     size: 1Gi
     storageClassName: ""
+    # Access modes of the claim; ReadWriteMany lets other pods read or add uploads.
+    accessModes:
+      - ReadWriteOnce
     # Specify an existing PVC to bind. The other values are then ignored.
     existingClaim: ""
     annotations: {}
diff --git a/wiki/Install-Helm.md b/wiki/Install-Helm.md
index a8fa64102..b51846b9b 100644
--- a/wiki/Install-Helm.md
+++ b/wiki/Install-Helm.md
@@ -190,6 +190,17 @@ persistence:
     size: 1Gi     # uploaded files — increase if you expect large media uploads
 ```
 
+Both claims are `ReadWriteOnce` by default. Set `persistence.data.accessModes` or `persistence.uploads.accessModes` to change that, for example so a backup container in another pod can mount the volume:
+
+```yaml
+persistence:
+  data:
+    accessModes:
+      - ReadWriteMany
+```
+
+> **Warning:** A `ReadWriteMany` data volume is only safe for pods that read it. SQLite needs every process that writes `travel.db` on the same host, so a second writer over a network filesystem corrupts the database. Keep `updateStrategy: Recreate` either way.
+
 ### Security Context
 
 ```yaml