tiflash: add upgrade.md doc

TOC.md

@@ -309,6 +309,7 @@
     - [Deploy a TiFlash Cluster](/reference/tiflash/deploy.md)
     - [Use TiFlash](/reference/tiflash/use-tiflash.md)
     - [Monitor TiFlash](/reference/tiflash/monitor.md)
+    - [Upgrade Nodes](/reference/tiflash/upgrade.md)
     - [Configure TiFlash](/reference/tiflash/configuration.md)
   + TiDB Binlog
     - [Overview](/reference/tidb-binlog/overview.md)

reference/tiflash/upgrade.md

@@ -0,0 +1,30 @@
+---
+title: Upgrade TiFlash Nodes
+summary: Learn how to upgrade TiFlash nodes.
+category: reference
+---
+
+# Upgrade TiFlash Nodes
+
+To upgrade TiFlash nodes, take the following steps:
+
+1. Download the new TiFlash binary to the Control Machine by either of the following two methods:
+
+    - Download the latest TiDB Ansible, or update the TiDB Ansible git repository by running the `git pull` command. Then run the `ansible-playbook local_prepare.yml` command.
+    - Manually download TiFlash binary and overwrite `resource/bin/tiflash`.
+
+2. Rolling upgrade TiFlash:
+
+    {{< copyable "shell-regular" >}}
+
+    ```shell
+    ansible-playbook rolling_update.yml --tags tiflash
+    ```
+
+3. Rolling upgrade the TiDB monitoring component:
+
+    {{< copyable "shell-regular" >}}
+
+    ```shell
+    ansible-playbook rolling_update_monitor.yml
+    ```