Database Reference
In-Depth Information
%
hdfs dfsadmin -refreshNodes
%
yarn rmadmin -refreshNodes
7. Remove the nodes from the
slaves
file.
Upgrades
Upgrading a Hadoop cluster requires careful planning. The most important consideration
is the HDFS upgrade. If the layout version of the filesystem has changed, then the upgrade
will automatically migrate the filesystem data and metadata to a format that is compatible
with the new version. As with any procedure that involves data migration, there is a risk
of data loss, so you should be sure that both your data and the metadata are backed up (see
Part of the planning process should include a trial run on a small test cluster with a copy
of data that you can afford to lose. A trial run will allow you to familiarize yourself with
the process, customize it to your particular cluster configuration and toolset, and iron out
any snags before running the upgrade procedure on a production cluster. A test cluster
also has the benefit of being available to test client upgrades on. You can read about gen-
eral compatibility concerns for clients in the following sidebar.
