project2B中peer storage内提到, “simply save all log entries at raft.Ready.Entries
to raftdb and delete any previously appended log entries which will never be committed” 这里如何判断哪些entries是需要删除的呢?
已经append的log应该都是stable的,如果是删除所有 index > last index of raft.Ready.Entries , 为什么不等到下一次ready来了直接对已有的index进行覆盖呢?