hadoop dfsadmin -report

用这个命令可以快速定位出哪些节点down掉了，HDFS的容量以及使用了多少，以及每个节点的硬盘使用情况。

当然NameNode有个http页面也可以查询，但是这个命令的输出更适合我们的脚本监控dfs的使用状况

Configured Capacity: 77209395855360 (70.22 TB)
Present Capacity: 76079914600683 (69.19 TB)
DFS Remaining: 60534707015680 (55.06 TB)
DFS Used: 15545207585003 (14.14 TB)
DFS Used%: 20.43%

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Datanodes available: 107 (109 total, 2 dead)

Name: 172.16.218.232:50010
Rack: /lg/dminterface0
Decommission Status : Normal
Configured Capacity: 1259272216576 (1.15 TB)
DFS Used: 185585852416 (172.84 GB)
Non DFS Used: 39060951040 (36.38 GB)
DFS Remaining: 1034625413120(963.57 GB)
DFS Used%: 14.74%
DFS Remaining%: 82.16%
Last contact: Wed Nov 18 10:19:44 CST 2009

Name: 172.16.216.126:50010
Rack: /lg/dminterface2
Decommission Status : Normal
Configured Capacity: 661261402112 (615.85 GB)
DFS Used: 123147280384 (114.69 GB)
Non DFS Used: 8803852288 (8.2 GB)
DFS Remaining: 529310269440(492.96 GB)
DFS Used%: 18.62%
DFS Remaining%: 80.05%
Last contact: Wed Nov 18 10:19:46 CST 2009