Book Image

Mastering Ceph

By : Nick Fisk
Book Image

Mastering Ceph

By: Nick Fisk

Overview of this book

Mastering Ceph covers all that you need to know to use Ceph effectively. Starting with design goals and planning steps that should be undertaken to ensure successful deployments, you will be guided through to setting up and deploying the Ceph cluster, with the help of orchestration tools. Key areas of Ceph including Bluestore, Erasure coding and cache tiering will be covered with help of examples. Development of applications which use Librados and Distributed computations with shared object classes are also covered. A section on tuning will take you through the process of optimisizing both Ceph and its supporting infrastructure. Finally, you will learn to troubleshoot issues and handle various scenarios where Ceph is likely not to recover on its own. By the end of the book, you will be able to successfully deploy and operate a resilient high performance Ceph cluster.
Table of Contents (12 chapters)

What is a bloom filter

A bloom filter is used in Ceph to provide an efficient way of tracking whether an object is a member of a HitSet without having to individually store the access status of each object. It is probabilistic in nature, and although it can return false positives, it will never return as false negative. This means that when querying a bloom filter, it may report that an item is present when it is not, but it will never report that an item is not present when it is.

Ceph's use of bloom filters allows it to efficiently track the accesses of millions of objects without the overhead of storing every single access. In the event of a false positive, it could mean that an object is incorrectly promoted; however, the probability of this happening combined with the minimal impact is of little concern.