Update docs, add some FAQ (#454)

Signed-off-by: wayblink <[email protected]>

README.md

@@ -13,18 +13,17 @@ The Milvus-backup process has negligible impact on the performance of Milvus. Mi
 
 * Download binary from [release page](https://github.com/zilliztech/milvus-backup/releases). Usually the latest is recommended.
 
-For Mac: 
-* Use [homebrew](https://brew.sh/) to install
+* Use [homebrew](https://brew.sh/) to install on Mac
   ```shell
   brew install zilliztech/tap/milvus-backup
   ```
 
-## Get started
+## Usage
 
 Milvus-backup provides command line and API server for usage.
 
-### Config
-In order to use Milvus-Backup, access to Milvus proxy and Minio cluster is required. Configuration settings related to this access can be edited in `backup.yaml`.
+### Configuration
+In order to use Milvus-Backup, access to Milvus proxy and Minio cluster is required. Configuration settings related to this access can be edited in [backup.yaml](configs/backup.yaml).
 
 > [!NOTE]
 >
@@ -80,14 +79,20 @@ The server will listen on port 8080 by default. However, you can change it by us
 
 We offer a [demo](docs/user_guide/api_demo.md) of the key APIs; however, please refer to the Swagger UI for the most up-to-date usage details, as the demo may occasionally become outdated.
 
-### swagger UI
+#### swagger UI
 
 We offer access to our Swagger UI, which displays comprehensive information for our APIs. To view it, simply go to
 
 ```
 http://localhost:8080/api/v1/docs/index.html
 ```
 
+### Advanced feature
+
+1. [Cross Storage Backup](docs/user_guide/cross_storage.md): Data is read from the source storage and written to a different storage through the Milvus-backup service. Such as, S3 -> local, S3 a -> S3 b. 
+
+2. [RBAC Backup&Restore](docs/user_guide/rbac.md): Enable backup and restore RBAC meta with extra parameter.
+
 
 ## Development
 

docs/user_guide/cross_storage.md

@@ -90,3 +90,23 @@ minio:
   # However, if they are the same but belong to different services, you must manually set this option to `true`.
   crossStorage: "true"
 ```
+
+## FAQ
+
+Q: 
+```
+What is the meaning of the option `crossStorage`. 
+
+Even if the storageType is the same, does it mean we need to set crossStorage to true when minio.address and backupaddress are different? 
+```
+
+A:
+```
+The crossStorage option determines how data is transferred:
+
+When set to True, data is transferred via read and write operations managed by the milvus-backup process.
+
+When set to False, data is directly copied using the storage system’s COPY API, bypassing the milvus-backup process.
+
+Use crossStorage based on whether the two addresses are accessible to each other through the COPY API.
+```