Book Image

Learning Ceph - Second Edition

By : Karan Singh, Vaibhav Bhembre, Anthony D'Atri
Book Image

Learning Ceph - Second Edition

By: Karan Singh, Vaibhav Bhembre, Anthony D'Atri

Overview of this book

Learning Ceph, Second Edition will give you all the skills you need to plan, deploy, and effectively manage your Ceph cluster. You will begin with the first module, where you will be introduced to Ceph use cases, its architecture, and core projects. In the next module, you will learn to set up a test cluster, using Ceph clusters and hardware selection. After you have learned to use Ceph clusters, the next module will teach you how to monitor cluster health, improve performance, and troubleshoot any issues that arise. In the last module, you will learn to integrate Ceph with other tools such as OpenStack, Glance, Manila, Swift, and Cinder. By the end of the book you will have learned to use Ceph effectively for your data storage requirements.
Table of Contents (18 chapters)
Title Page
Credits
About the Authors
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface

Placement groups


In the previous section, we described what objects in Ceph are and how we can access them. Ceph distributes objects pseudo-randomly to storage devices based on predefined data assignment policies. The assignment policy uses a novel placement algorithm called CRUSH to choose a probabilistically balanced distribution of objects throughout the cluster. This ensures that devices are presented with a nearly uniform storage and workload distribution for most use-cases. When a cluster is expanded by adding new storage or old/failed devices are removed, it is necessary to restore balance by migrating data to restore the configured replication policies. Since this data movement is kept a minimum, augmenting an existing cluster is significantly less cumbersome compared to the use of other, less-sophisticated placement algorithms. CRUSH will be explored in detail in the next section.

When Ceph receives requests to store data, it needs to determine the set designated objects the requests...