我们是一次写入还是分多次写入？ 如果是一次写入的话 对于大文件 如果有哪里写错了 就要重写。 所以我们是将之分块：
那么每一个chunk是如何写入server的呢？ 是直接写道chunk server里面还是说先和master沟通 然后再写入chunk server
when what should we do when we have to modify the large chunk which is already divide into chunks? there are few aspects we should consider about: which chunk should we modify? what should we do if the chunk become larger or smaller after modification? 解决方案：因为每个文件我们写的少 读得多 所以我们删掉这个文件 然后重新写入修改后的
