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

Tiering modes


There are a number of tiering modes that determine the precise actions of how Ceph reacts to the contents of the HitSets. However, in most cases, the writeback mode will be used. The available modes for use in tiering are writeback, forward, read-forward, proxy, and read-proxy. There are brief descriptions of the available modes and how they act.

Writeback

In writeback mode, data is promoted to the top-level tier by both reads and writes depending on how frequently accessed the object are. Objects in the top-level tier can be modified, and dirty objects will be flushed to the pool at a later date. If an object needs to be read or written to in the bottom tier and the bottom pool supports it, then Ceph will try and directly proxy the operation that has a minimal impact on latency.

Forward

The forward mode simply forwards all requests from the top tier to the base tier without doing any promotions. It should be noted that a forward causes OSD to tell the client to resend the request...