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

Recovering from a complete monitor failure


In the unlikely event that you lose all of your monitors, all is not lost. You can rebuild the monitor database from the contents of the OSDs by the use of the ceph-objectstore tool.

To set the scenario, we will assume that an event has occurred and has corrupted all three monitors, effectively leaving the Ceph cluster inaccessible. To recover the cluster, we will shut down two of the monitors and leave a single failed monitor running. We will then rebuild the monitor database, overwrite the corrupted copy, and then restart the monitor to bring the Ceph cluster back online.

The objectstore tool needs to be able to access every OSD in the cluster to rebuild the monitor database; in this example, we will use a script, which will connect via ssh to access the OSD data. As the OSD data is not accessible by every user, we will use the root user to log in to the OSD hosts. By default, most Linux distributions will not allow remote, password-based root logins...