Using Erasure Coding for Existing Data

You must set a supported EC policy for a directory and copy the existing data to the directory. Since Erasure Coding does not apply to existing data, we need to recreate the directory and then move the data to an erasure coding enabled directory.

Create a new directory or choose an existing directory.

1. View the supported EC policies.

hdfs ec -listPolicies

2. Enable a supported EC policy.

hdfs ec -enablePolicy -policy <policy>

3. Set the EC policy for the directory you want to use.

hdfs ec -setPolicy -path <directory> [-policy <policyName>]

• path: This is mandatory. Specify the HDFS directory you want to apply the EC policy to.
• policy: This is optional. The EC policy you want to use for the directory you specified. If you do not provide this parameter, the EC policy you specified in the Default Policy when Setting Erasure Coding setting from Ambari is used.