Book Image

Mastering Ceph, - Second Edition

By : Nick Fisk
Book Image

Mastering Ceph, - Second Edition

By: Nick Fisk

Overview of this book

Ceph is an open source distributed storage system that is scalable to Exabyte deployments. This second edition of Mastering Ceph takes you a step closer to becoming an expert on Ceph. You’ll get started by understanding the design goals and planning steps that should be undertaken to ensure successful deployments. In the next sections, you’ll be guided through setting up and deploying the Ceph cluster with the help of orchestration tools. This will allow you to witness Ceph’s scalability, erasure coding (data protective) mechanism, and automated data backup features on multiple servers. You’ll then discover more about the key areas of Ceph including BlueStore, erasure coding and cache tiering with the help of examples. Next, you’ll also learn some of the ways to export Ceph into non-native environments and understand some of the pitfalls that you may encounter. The book features a section on tuning that will take you through the process of optimizing both Ceph and its supporting infrastructure. You’ll also learn to develop applications, which use Librados and distributed computations with shared object classes. Toward the concluding chapters, you’ll learn to troubleshoot issues and handle various scenarios where Ceph is not likely to recover on its own. By the end of this book, you’ll be able to master storage management with Ceph and generate solutions for managing your infrastructure.
Table of Contents (18 chapters)
Free Chapter
1
Section 1: Planning And Deployment
6
Section 2: Operating and Tuning
13
Section 3: Troubleshooting and Recovery

Full OSDs

By default, Ceph will warn us when OSD utilization approaches 85%, and it will stop writing I/O to the OSD when it reaches 95%. If, for some reason, the OSD completely fills up to 100%, the OSD is likely to crash and will refuse to come back online. An OSD that is above the 85% warning level will also refuse to participate in backfilling, so the recovery of the cluster may be impacted when OSDs are in a near-full state.

Before covering the troubleshooting steps around full OSDs, it is highly recommended that you monitor the capacity utilization of your OSDs, as described in Chapter 8, Monitoring Ceph. This will give you advanced warning as OSDs approach the near_full warning threshold.

If you find yourself in a situation where your cluster is above the near-full warning state, you have two options:

  • Add some more OSDs
  • Delete some data

However, in the real world, both...