add upgrade document

docs/user-guides/upgrade-cluster.md

@@ -0,0 +1,137 @@
+# Upgrade Vald cluster
+
+Before this document, we recommend reading [the configuration document](../user-guides/configuration.md) first.
+
+## Update Configuration
+
+When you'd like to update the configuration for the Vald cluster, you need to edit your configuration file and apply it according to your deployment method.
+Please refer to one of the sections below according to your deployment method.
+
+<div class="caution">
+If each Vald Agent already has the indexes and uses the backup feature, please DO NOT edit the dimension and the distance type to avoid initContainer error.<BR>
+(Each Vald Agent will restore from backup data when backup when performing a rolling update)
+</div>
+
+<div class="warn">
+The indexes will be clear when performing a rolling update if each Vald Agent already has the indexes and does not use the backup.
+</div>
+
+### Using Helm for deployment
+
+The configuration file is `values.yaml`. (https://helm.sh/docs/chart_template_guide/values_files/)
+
+
+You can edit your `values.yaml` and update your Vald cluster by following steps:
+1. Edit `values.yaml`.
+1. Update with Helm command. 
+
+    ```bash
+    helm upgrade <NAME> vald/vald --values <YOUR VALUES FILE PATH>
+    # e.g., helm upgrade vald vald/vald --values valeus.yaml
+    ```
+
+### Using vald-helm-operator
+
+There are two configuration files:
+- `vhor.yaml` for vald-helm-operator
+- `vr.yaml` for the Vald cluster
+
+If you don't need to update the `vald-helm-operator`, please skip step.1 and step.2.
+The Vald cluster will be updated by the following steps:
+1. Edit `vhor.yaml`.
+1. Apply `vhor.yaml`.
+
+    ```bash
+    kubectl apply -f <VHOR YAML FILE PATH>
+    # e.g., kubectl apply -f vhor.yaml 
+    ```
+
+1. Edit `vr.yaml`.
+1. Apply `vr.yaml`.
+
+    ```bash
+    kubectl apply -f <VR YAML FILE PATH>
+    # e.g., kubectl apply -f vr.yaml 
+    ```
+
+## Upgrade Vald version
+
+We recommend using the latest Vald version.
+
+If your Vald cluster uses an old version and you'd like to upgrade the Vald version, you can upgrade by the following sections.
+Please refer to one of the sections below according to your deployment method.
+
+<div class="caution">
+When the upgrade request is applied, Kubernetes will perform a rolling update.
+If your Vald cluster does not apply backup, the index will be cleared by a rolling update.<BR>
+In addition, if each Vald Agent already has the indexes and uses the backup feature, please DO NOT edit the dimension and the distance type to avoid initContainer error.
+(Each Vald Agent will restore from backup data when backup when performing a rolling update)
+</div>
+
+### Using Helm for deployment
+
+Using the `Helm` command for the deployment of the Vald cluster, the upgrading steps are below.
+
+1. Update Helm repo
+
+    ```bash
+    helm repo update <NAME> https://vald.vdaas.org/charts
+    # e.g., helm repo update vald https://vald.vdaas.org/charts
+    ```
+
+1. Edit `values.yaml`
+    - We recommend setting a specific version as an image tag.
+
+        ```yaml
+        defaults:
+        ...
+          image:
+            tag: v1.5.6 # set a new version
+        ...
+        ```
+
+1. Apply `values.yaml`
+
+    ```bash
+    helm upgrade <NAME> vald/vald --values <YOUR VALUES FILE PATH>
+    # e.g., helm upgrade vald vald/vald --values valeus.yaml
+    ```
+
+### Using vald-helm-operator
+
+The upgrading steps are below if you use `vald-helm-operator` for the deployment.
+
+1. Upgrade CRDs
+
+    ```bash
+    kubectl replace -f https://raw.githubusercontent.com/vdaas/vald/<VERSION>/charts/vald-helm-operator/crds/valdrelease.yaml
+    kubectl replace -f https://raw.githubusercontent.com/vdaas/vald/<VERSION>/charts/vald-helm-operator/crds/valdhelmoperatorrelease.yaml
+    ```
+
+1. Update `vhor`
+
+    ```bash
+    kubectl patch vhor vhor-release -p '{"spec":{"image":{"tag":"<VERSION>"}}}'
+    ```
+
+    - Also, you can upgrade manually by editing `vhor.yaml` and applying it.
+
+1. Edit `vr.yaml`
+    - We recommend setting a specific version as an image tag.
+
+        ```yaml
+        ...
+        spec:
+          defaults:
+            ...
+            image:
+              tag: v1.5.6 # set a new version
+            ...
+        ```
+
+1. Apply `vr.yaml`
+
+    ```bash
+    kubectl apply -f <VR YAML FILE PATH>
+    # e.g., kubectl apply -f vr.yaml 
+    ```