Book Image

Ceph: Designing and Implementing Scalable Storage Systems

By : Michael Hackett, Vikhyat Umrao, Karan Singh, Nick Fisk, Anthony D'Atri, Vaibhav Bhembre
Book Image

Ceph: Designing and Implementing Scalable Storage Systems

By: Michael Hackett, Vikhyat Umrao, Karan Singh, Nick Fisk, Anthony D'Atri, Vaibhav Bhembre

Overview of this book

This Learning Path takes you through the basics of Ceph all the way to gaining in-depth understanding of its advanced features. You’ll gather skills to plan, deploy, and manage your Ceph cluster. After an introduction to the Ceph architecture and its core projects, you’ll be able to set up a Ceph cluster and learn how to monitor its health, improve its performance, and troubleshoot any issues. By following the step-by-step approach of this Learning Path, you’ll learn how Ceph integrates with OpenStack, Glance, Manila, Swift, and Cinder. With knowledge of federated architecture and CephFS, you’ll use Calamari and VSM to monitor the Ceph environment. In the upcoming chapters, you’ll study the key areas of Ceph, including BlueStore, erasure coding, and cache tiering. More specifically, you’ll discover what they can do for your storage system. In the concluding chapters, you will develop applications that use Librados and distributed computations with shared object classes, and see how Ceph and its supporting infrastructure can be optimized. By the end of this Learning Path, you'll have the practical knowledge of operating Ceph in a production environment. This Learning Path includes content from the following Packt products: • Ceph Cookbook by Michael Hackett, Vikhyat Umrao and Karan Singh • Mastering Ceph by Nick Fisk • Learning Ceph, Second Edition by Anthony D'Atri, Vaibhav Bhembre and Karan Singh
Table of Contents (27 chapters)
Title Page
About Packt
Contributors
Preface
Index

Understanding the CRUSH mechanism


When it comes to data storage and management, Ceph uses the CRUSH algorithm, which is an intelligent data distribution mechanism of Ceph. As we discussed in the last recipe, traditional storage systems use a central metadata/index table to know where the user's data is stored. Ceph, on the other hand, uses the CRUSH algorithm to deterministically compute where the data should be written to or read from. Instead of storing metadata, CRUSH computes metadata on demand, thus removing the need for a centralized server/gateway or broker. It empowers Ceph clients to compute metadata, also known as CRUSH lookup, and communicates with OSDs directly.

For a read/write operation to Ceph clusters, clients first contact a Ceph monitor and retrieve a copy of the cluster map, which is inclusive of five maps, namely the monitor, OSD, MDS, and CRUSH and PG maps; we will cover these maps later in this chapter. These cluster maps help clients know the state and configuration...