Ceph: A Reliable And Scalable Distributed Filesystem with Sage Weil - Episode 40

Jul 16, 2018

Sage Weil, creator and lead maintainer of Ceph and Red Hat engineer, talks about the origins and architecture of a scalable distributed storage system. He covers object, block, and file interfaces. He explains fault-tolerance, daemon roles, multi-site replication, Kubernetes integration, hardware sizing, and plans for performance and multi-cloud data services.

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ANECDOTE

Ceph Began As An Academic Project Turned Production

Sage Weil started Ceph as a research project at UC Santa Cruz focused on petabyte-scale HPC storage.
After years of development it later became production-ready and was used at DreamHost for an S3-compatible service and block storage around 2011–2012.

INSIGHT

RADOS Provides A Single Resilient Underlayer

Ceph's architecture centers on an underlying object layer (RADOS) designed to avoid single points of failure and scale with unreliable commodity hardware.
Building block and file interfaces on top of RADOS allowed different optimizations per API while sharing a single resilient storage substrate.

ADVICE

Require Monitor Quorum To Prevent Split Brain

Use a monitor quorum to avoid split-brain: Ceph requires a majority of monitors online to form a consistent view and allow writes.
This lets the system avoid heavyweight consensus on every IO and instead use Paxos only for cluster membership decisions.

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Summary

When working with large volumes of data that you need to access in parallel across multiple instances you need a distributed filesystem that will scale with your workload. Even better is when that same system provides multiple paradigms for interacting with the underlying storage. Ceph is a highly available, highly scalable, and performant system that has support for object storage, block storage, and native filesystem access. In this episode Sage Weil, the creator and lead maintainer of the project, discusses how it got started, how it works, and how you can start using it on your infrastructure today. He also explains where it fits in the current landscape of distributed storage and the plans for future improvements.

Preamble

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Your host is Tobias Macey and today I’m interviewing Sage Weil about Ceph, an open source distributed file system that supports block storage, object storage, and a file system interface.

Interview

Introduction
How did you get involved in the area of data management?
Can you start with an overview of what Ceph is?
- What was the motivation for starting the project?
- What are some of the most common use cases for Ceph?

There are a large variety of distributed file systems. How would you characterize Ceph as it compares to other options (e.g. HDFS, GlusterFS, LionFS, SeaweedFS, etc.)?

Given that there is no single point of failure, what mechanisms do you use to mitigate the impact of network partitions?
- What mechanisms are available to ensure data integrity across the cluster?

How is Ceph implemented and how has the design evolved over time?

What is required to deploy and manage a Ceph cluster?
- What are the scaling factors for a cluster?
- What are the limitations?

How does Ceph handle mixed write workloads with either a high volume of small files or a smaller volume of larger files?

In services such as S3 the data is segregated from block storage options like EBS or EFS. Since Ceph provides all of those interfaces in one project is it possible to use each of those interfaces to the same data objects in a Ceph cluster?

In what situations would you advise someone against using Ceph?

What are some of the most interested, unexpected, or challenging aspects of working with Ceph and the community?

What are some of the plans that you have for the future of Ceph?

Contact Info

Email
@liewegas on Twitter
liewegas on GitHub

Parting Question

From your perspective, what is the biggest gap in the tooling or technology for data management today?

Links

The intro and outro music is from The Hug by The Freak Fandango Orchestra / CC BY-SA

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