Specifying the Racks for Hosts
Cloudera Manager includes internal rack awareness scripts, but you must specify the racks where the hosts in your cluster are located. If your cluster contains more than 10 hosts, Cloudera recommends that you specify the rack for each host. HDFS and MapReduce will automatically use the racks you specify.
Cloudera Manager supports nested rack specifications. For example, you could specify the rack /rack1, but you could also specify /group5/rack3 to indicate the third rack in the fifth group.
Currently, due to a Hadoop limitation, all hosts in a cluster should have the same number of path components in their rack specifications.
To specify the racks for hosts:
- Click the Hosts tab.
- Select the host(s) for a particular rack, such as all hosts for /rack123. Use shift-click to select multiple hosts at a time.
- Click Assign Rack.
- Enter a rack name or ID that starts with a slash /, such as /rack123 or /aisle1/rack123, and then click Set Rack.
After assigning racks, consider restarting affected services as described in Starting, Stopping, and Restarting Services. Rack assignments are not automatically updated for running services.