There's a bit of an issue if you have no data in your HDFS -- 0 blocks out of 0 is considered 100% reported, so NN leaves safe mode even if there are no DNs talking to it yet.
For a fix, please see HDFS-528, included in Cloudera's CDH2. Thanks -Todd On Fri, Mar 19, 2010 at 10:29 AM, Bill Habermaas <b...@habermaas.us> wrote: > 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:nklos...@ecn.purdue.edu] > Sent: Friday, March 19, 2010 1:21 PM > To: common-user@hadoop.apache.org > 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 > > > -- Todd Lipcon Software Engineer, Cloudera
