Here it is https://issues.apache.org/jira/browse/HADOOP-4539. Konstantin talked about it in a May 27 mail in the thread "Setting up another machine as secondary node".
J-D On Fri, Jun 19, 2009 at 2:39 PM, Andrew Wharton <[email protected]>wrote: > Does anybody know the state of the Backupnamenode scheme that is > referenced here? I am looking for a Jira ticket that might give me some > more insight into the timeline for release. The hadoop-general email > list doesn't seem to have any information about this issue, which is > kind of worrying... > > TIA. > > -- Andrew > > On Tue, 2009-06-02 at 16:57 +0200, ext Jean-Daniel Cryans wrote: > > Andrew, > > > > I think you are confusing some components of the whole stack here. The > > Namenode is the master for HDFS just like the HMaster is the master > > for HBase. Hadoop is 2 things : HDFS and an implementation of > > MapReduce which also has a master, the JobTracker. HBase sits on all > > that. > > > > So with regards with what's fixed, the HMaster SPOF is fixed for 0.20. > > The Namenode in 0.20 is still a SPOF. That means, if you want HA, you > > should get a really reliable machine for the Namenode but you can put > > the HMaster on any nodes you want. > > AFAIK, there is a BackupNamenode in Hadoop 0.21 that serves as a > > Namenode failover. > > >
