Before You Begin
- Before upgrading, be sure to read about the latest Incompatible Changes and Known Issues and Work Arounds in CDH4 in the CDH4 Release Notes.
- If you are upgrading a cluster that is part of a production system, be sure to plan ahead. As with any operational work, be sure to reserve a maintenance window with enough extra time allotted in case of complications. The Hadoop upgrade process is well understood, but it is best to be cautious. For production clusters, Cloudera recommends allocating up to a full day maintenance window to perform the upgrade, depending on the number of hosts, the amount of experience you have with Hadoop and Linux, and the particular hardware you are using.
- If you are running a pseudo-distributed (single-machine) Apache Hadoop cluster, Cloudera recommends that you copy your data off the cluster, remove the old CDH release, install Hadoop from CDH4, and then restore your data.
- If you have a multi-machine cluster, read the following sections to learn how to upgrade your cluster to CDH4.
: If you are using a high-availability (HA) configuration
on CDH4 Beta 1:
You must unconfigure HA before you proceed. See Upgrading an HA Configuration to the Latest Release.