Hi Björn, > has it ever happened that a migration of persistent data has been needed (or > automatically executed) when updating a Hadoop installation within a release? > If so, where could I find information regarding such needed migration?
Normally, when you change the minor release, you need to upgrade HDFS (http://hadoop.apache.org/docs/stable/hdfs_user_guide.html#Upgrade+and+Rollback). This will happen when you switch major branches. > I would be interested because the runtime of such migration would probably > depend on the amount of managed data and had to be planned. Depends how much data you've stored. Michael has written a excellent blog post about: http://www.michael-noll.com/blog/2011/08/23/performing-an-hdfs-upgrade-of-an-hadoop-cluster/ Cheers, Alex -- Alexander Alten-Lorenz http://mapredit.blogspot.com German Hadoop LinkedIn Group: http://goo.gl/N8pCF
