当你有一个正在运行的组需要升级，但你需要保持该组在线以服务你的应用程序时，你需要考虑升级的方法。本节描述了在线升级中涉及的不同要素，以及升级组的各种方法。When you have a group running which you want to upgrade but you need to keep the group online to serve your application, you need to consider your approach to the upgrade. This section describes the different elements involved in an online upgrade, and various methods of how to upgrade your group.