RPO corresponds to the maximum quantity of data that can be acceptably lost when a breakdown occurs.

RTO corresponds to the maximum acceptable duration of the interruption.

The service-level agreement (SLA) is a contract that specifies service levels.

描述                              通俗叫法     可用性级别     年度停机时间
基本可用性                          2个9           99%          87.6小时
较高可用性                          3个9           99.9%        8.8小时
具有故障自动恢复能力的可用性        4个9           99.99%       53分钟
极高可用性                          5个9           99.999%      5分钟