Add legacy for origin cluster.

Author: winlinvip

i18n/en-us/docusaurus-plugin-content-docs/current/doc/origin-cluster.md

@@ -58,6 +58,11 @@ cd proxy-go && make
 We will support the Docker image in the future, or integrate the proxy server into the Oryx 
 project.
 
+## Legacy
+
+From SRS 7.0+, the new Origin Cluster is based on proxy server, not the old MESH based SRS servers.
+However, if you want to use the old origin cluster, you can switch to SRS 6.0.
+
 ## RTMP Origin Cluster
 
 To use the RTMP origin cluster, you need to deploy the proxy server and the origin server. 

i18n/zh-cn/docusaurus-plugin-content-docs/current/doc/origin-cluster.md

@@ -52,6 +52,11 @@ cd proxy-go && make
 
 我们将在未来支持Docker镜像，或将proxy server集成到Oryx项目中。
 
+## Legacy
+
+从SRS 7.0及以上版本开始，新的Origin集群基于proxy server，而不是旧的MESH架构SRS服务器。
+如果你需要使用旧的Origin集群，可以切换到SRS 6.0版本。
+
 ## RTMP Origin Cluster
 
 要使用RTMP源站集群，您需要部署proxy server和源服务器。首先，启动proxy server：