Hi, I'm working on upgrading my cluster from CDH3u5 to CDH4. Trying to do the upgrade in place rather than creating a new cluster and migrating over.
Doing this on a test cluster right now, but ran into an issue - First I uninstalled the CDH3 packages and installed the CDH4 ones, then upgraded the namenode and then started the namenode service. Then I started the datanode service on one of the data nodes and the machine started filling up quickly. It seems like it's re-writing the data into a new format. Is this correct, does the upgrade process rewrite the old data into a new format? And if so, that means I need a lot of free space on the data nodes that are being upgrade? Thanks
