feature(doc): backup minio data (#627)

* feature(doc): backup minio data doc

Signed-off-by: soulseen <zhuxiaoyang1996@gmail.com>

* feature(doc): get minio access from secret

Signed-off-by: soulseen <zhuxiaoyang1996@gmail.com>

As it's doc PR, directly merged.

docs/LCM/backup-minio-data.md

@@ -2,4 +2,48 @@
 
 Documentation shown here guides you how to backup the Minio data.
 
-TBD
+## Prerequisites
+
+1. You need to install [mc]( https://docs.min.io/docs/minio-client-complete-guide.html) that is the MinIO CLI.
+
+2. Get the `access_key` and `secret_key` of MinIO.
+
+    ```shell
+    $ kubectl get secret minio-access-secret -n cluster-sample-ns -o jsonpath='{.data.accesskey}' | base64 --decode
+    admin
+    $ kubectl get secret minio-access-secret -n cluster-sample-ns -o jsonpath='{.data.secretkey}' | base64 --decode
+    minio123
+    ```
+
+3. Please make sure you have the correct MinIO address to access.
+
+## Backup
+
+### Step 1
+
+Create the directory to storage Harbor Data in the backup pod, please make sure you have the Read/Write Permissions.
+
+```shell
+mkdir {minio_backup_directory}
+```
+
+### Step 2
+
+Setup mc config.
+
+```shell
+mc --insecure -C {minio_backup_directory} config host add minio \ http(s)://{minio_address}:9000 {minio_access_key} {minio_secret_key}
+```
+
+### Step 3
+
+Start backup minio data
+
+```shell
+mc --insecure -C {minio_backup_directory} \  
+cp -r minio/harbor {minio_backup_directory}
+```
+
+### Step 4
+
+Make sure that all data are backuped in the {minio_backup_directory}.