Dear Jeff, First, thank you very much for your selfless help! For these three computers, it just seems like they are sharing a same disk area. I don't know whether they will redundant copy data or other way. Any way, let me use an example to explain that. When I create any file, e.g., foo in one of these computers, A. Then from the other two nodes, B and C, I can see the same file foo.
Below is the log in my system, The success one records like this, you can see that this machine have format that directory, 2010-03-11 17:17:12,689 INFO org.apache.hadoop.hdfs.server.common.Storage: Storage directory $HOME/data/dir is not formatted. 2010-03-11 17:17:12,689 INFO org.apache.hadoop.hdfs.server.common.Storage: Formatting ... The fail node then records like this, he can't use the same directory, because this directory is locked. 2010-03-11 17:17:09,176 INFO org.apache.hadoop.hdfs.server.common.Storage: Cannot lock storage $HOME/data/dir. The directory is already locked. 2010-03-11 17:17:09,288 ERROR org.apache.hadoop.hdfs.server.datanode.DataNode: java.io.IOException: Cannot lock storage $HOME/data/dir. The directory is already locked. May be these three directories are on independent disks, but from hadoop's point, it's a same directory, and only can be locked once. So that why I can't deploy Hadoop. Best Regards welman Lu
