也就是说备份时仍可以提交事务，且备份过程不会破坏事务的一致性，具体来说：
当备份过程完成时：
1.已提交了的事务将在副本数据中得到体现
2.未提交的事务，在副本中会被回滚，数据仍然保持一致性
原文是这样的：
The term consistent state means that all transactions that are committed while the backup is being performed are applied and all transactions that are not finished are rolled back.