Hadoop Storage Policies Management

Introduction

In this lab, you will learn how to master Hadoop Storage Policies, unlocking the secrets hidden within the vast Arabian Desert's golden sands. You'll embark on a journey where a wise sorcerer challenges you to harness the power of these policies, enabling efficient management of data storage in Hadoop. Gain invaluable skills to store and retrieve data across different tiers, optimizing both performance and cost-effectiveness.

Skills Graph

Understanding Storage Policies in Hadoop

In this step, you will learn about the concept of storage policies in Hadoop and how they can be used to manage data storage across different storage tiers.

Switch user to access Hadoop file system using su - hadoop command. Then, List the available storage policies:

hdfs storagepolicies -listPolicies

The output should display the default storage policies available in your Hadoop cluster. Here is a sample output:

Block Storage Policies:
	BlockStoragePolicy{PROVIDED:...}
	BlockStoragePolicy{COLD:...}
	BlockStoragePolicy{WARM:...}
	BlockStoragePolicy{HOT:...}

Storage policies allow you to define different storage tiers based on data access patterns, performance requirements, and cost considerations. For example, the "HOT" policy can be used for frequently accessed data, while the "COLD" policy can be used for archival data.

Set and Get Directory Storage Policy

In this step, you will learn how to set a specific storage policy for a directory in Hadoop.

First, create a new directory in HDFS:

hdfs dfs -mkdir /example

Next, set the specific storage policy for the /example directory to the "WARM" policy you created in the previous step:

hdfs storagepolicies -setStoragePolicy -path /example -policy WARM

This command sets the "WARM" storage policy as the specific policy for the /example directory and all its subdirectories and files.

You can verify the storage policy for the directory using the hdfs storagepolicies command:

hdfs storagepolicies -getStoragePolicy -path /example

The output should display the "WARM" policy as the storage policy for the /example directory.

Set and Get File Storage Policy

In this step, you will learn how to move existing data in Hadoop to a specific storage policy.

First, create a sample file in HDFS:

hdfs dfs -touchz /example/sample.txt

Next, check the current storage policy for the file:

hdfs storagepolicies -getStoragePolicy -path /example/sample.txt

The output should display the "WARM" storage policy, which is the default policy for the /example directory.

Now, let's move the sample.txt file to the "HOT" storage policy:

hdfs storagepolicies -setStoragePolicy -path /example/sample.txt -policy HOT

This command changes the storage policy for the sample.txt file to the "HOT" storage policy.

You can verify the new storage policy for the file using the hdfs storagepolicies command:

hdfs storagepolicies -getStoragePolicy -path /example/sample.txt

The output should now display the "HOT" policy for the sample.txt file.

Remove Storage Policy From a File

In this step, you will learn how to remove the storage policy for a specific file in Hadoop.

If you want to remove the storage policy for the /example/sample.txt file, you can use the hdfs storagepolicies command:

hdfs storagepolicies -unsetStoragePolicy -path /example/sample.txt

This command removes the storage policy for the /example/sample.txt file, so that the file no longer has an explicit storage policy, but instead inherits the policy of the directory in which it resides or adopts the cluster's default storage policy.

You can then use the hdfs command to confirm that the sample.txt file's storage policy has been removed:

hdfs storagepolicies -getStoragePolicy -path /example/sample.txt

The output should now show the "WARM" policy for the sample.txt file, i.e. the policy for the directory it resides in.

Summary

Congratulations! You have successfully mastered Hadoop Storage Policies, enabling effective management of data storage. With your newfound skills, you can optimize data storage and retrieval in Hadoop, ensuring efficiency and cost-effectiveness. Guided by the wise sorcerer, you've unlocked the secrets of storage policies, ready to tackle any data storage challenges that come your way.