Upgrading CDH 4
Use the instructions in this section to upgrade to a higher CDH 4 minor release, that is from CDH 4.a.x to CDH 4. b.y. For example, CDH 4.6.0 to CDH 4.7.1.
You can upgrade to CDH 4.1.3 (or higher) within the Cloudera Manager Admin Console, using parcels and an upgrade wizard. This vastly simplifies the upgrade process. Electing to upgrade using packages means that future upgrades will still need to be done manually. Upgrading to a CDH 4 release prior to CDH 4.1.3 is possible using packages, though upgrading to a more current release is strongly recommended.
If you use parcels, have a Cloudera Enterprise license, and have enabled HDFS high availability, you can perform a rolling upgrade that lets you avoid cluster downtime.
Before You Begin
- Before upgrading, be sure to read about the latest Incompatible Changes and Known Issues and Workarounds in the CDH 4 Release Notes.
- Read the Cloudera Manager 5 Release Notes.
- Ensure that the Cloudera Manager minor version is equal to or greater than the CDH minor version. For example:
Target CDH Version Minimum Cloudera Manager Version 5.0.5 5.0.x 5.1.4 5.1.x 5.4.1 5.4.x
- Run the Host Inspector and fix every issue.
- If using security, run the Security Inspector.
- Whenever upgrading Impala, whether in CDH or a standalone parcel or package, check your SQL against the newest reserved words listed in incompatible changes. If upgrading across multiple versions or in case of any problems, check against the full list of Impala keywords.
- Run hdfs fsck / and hdfs dfsadmin -report and fix every issue.
- Run hbase hbck.
- Review the upgrade procedure and reserve a maintenance window with enough time allotted to perform all steps. 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.
- To avoid lots of alerts during the upgrade process, you can enable maintenance mode on your cluster before you start the upgrade. This will stop email alerts and SNMP traps from being sent, but will not stop checks and configuration validations from being made. Be sure to exit maintenance mode when you have finished the upgrade in order to re-enable Cloudera Manager alerts.