logback 设置按天，文件切割大小，总共日志文件大小。

<configuration>  
  <appender name="ROLLING" class="ch.qos.logback.core.rolling.RollingFileAppender">  
    <file>mylog.txt</file>  
    <rollingPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedRollingPolicy">  
      <!-- rollover daily -->  
      <fileNamePattern>mylog-%d{yyyy-MM-dd}.%i.txt</fileNamePattern>  
       <!-- each file should be at most 100MB, keep 60 days worth of history, but at most 20GB -->  
       <maxFileSize>100MB</maxFileSize>      
       <maxHistory>60</maxHistory>  
       <totalSizeCap>20GB</totalSizeCap>  
    </rollingPolicy>  
    <encoder>  
      <pattern>%msg%n</pattern>  
    </encoder>  
  </appender>  
  
  
  <root level="DEBUG">  
    <appender-ref ref="ROLLING" />  
  </root>  
  
</configuration>