Hadoop列举NameNode 在管理 DataNode 过程中可能遇到的问题，NameNode采用什么策略解决了管理过程遇到的问题。
参考：https://blog.csdn.net/Allenzyg/article/details/106237636?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522166997378716782425619347%2522%252C%2522scm%2522%253A%252220140713.130102334.pc%255Fblog.%2522%257D&request_id=166997378716782425619347&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2~blog~first_rank_ecpm_v1~rank_v31_ecpm-23-106237636-null-null.nonecase&utm_term=hadoop&spm=1018.2226.3001.4450