At startup, the namenode goes into 'safe' mode to wait for all data nodes to send block reports on data they are holding. This is normal for hadoop and necessary to make sure all replicated data is accounted for across the cluster. It is the nature of the beast to work this way for good reasons.
Bill -----Original Message----- From: Nick Klosterman [mailto:[email protected]] Sent: Friday, March 19, 2010 1:21 PM To: [email protected] Subject: Why must I wait for NameNode? What is the namemode doing upon startup? I have to wait about 1 minute and watch for the namenode dfs usage drop from 100% otherwise the install is unusable. Is this typical? Is something wrong with my install? I've been attempting the Pseudo distributed tutorial example for a while trying to get it to work. I finally discovered that the namenode upon start up is 100% in use and I need to wait about 1 minute before I can use it. Is this typical of hadoop installations? This isn't entirely clear in the tutorial. I believe that a note should be entered if this is typical. This error caused me to get "WARN org.apache.hadoop.hdfs.DFSClient: DataStreamer Exception: SOMEFILE could only be replicated to 0 nodes, instead of 1" I had written a script to do all of the steps right in a row. Now with a 1 minute wait things work. Is my install atypical or am I doing something wrong that is causing this needed wait time. Thanks, Nick
