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

Using the Cephs object store tool


Hopefully, if you have followed best practice, your cluster is running with three replicas and is not configured with any dangerous configuration options. Ceph, in most cases, should be able to recover from any failure.

However, in the scenario where a number of OSDs go offline, a number of PGs and/or objects may become unavailable. If you are unable to reintroduce these OSDs back into the cluster to allow Ceph to recover them gracefully, then the data in those PGs is effectively lost. However, there is a possibility that the OSD is still readable to use the objectstore tool to recover the PGs contents. The process involves exporting the PGs from the failed OSDs and then importing the PGs back into the cluster. The objectstore tool does require that the OSDs internal metadata is still in a consistent state, so a full recovery is not guaranteed.

In order to demonstrate the use of the objectstore tool, we will shut down two of our three test cluster OSDs, and...