as described in http://www.google.com/url?sa=t&source=web&cd=1&ved=0CBgQFjAA&url=http%3A%2F%2Fhadoopblog.blogspot.com%2F2010%2F02%2Fhadoop-namenode-high-availability.html&ei=D4MkTsCrI8TRiALN4-mvAw&usg=AFQjCNFTIAn6ETjAxlC6s5u33sjTUARZQw&sig2=yIka9cpvn9qHvve95niefA
and in the recent FB paper, AvatarNode is a different solution as the BackUpNode/CheckpointNode feature, right? -----since the link above says: "The HDFS BackupNode is not available in 0.20, and upgrading our cluster to hadoop 0.20 is not a feasible option for us because .... ". if they are different, is the FB AvatarNode feature is open-sourced ? if so, is it a better or worse solution than the current BackUpNode/CheckpointNode in apache distribution? Thanks yang
