Learn Ceph - Real-world Use Cases & Patterns

#Introduction

Welcome to episode 20 of the Learn Ceph series! Throughout this series you've learned Ceph's features and how to operate it. This episode ties everything to the real world: how Ceph is actually used in production, proven architectural patterns, and how to plan capacity and cost.

Every organization uses Ceph differently — cloud providers use it for virtual block storage, enterprises use it for shared file services, and data platforms use it as S3 object storage. Studying these patterns helps you choose the right design for your own needs.

By the end of this episode you'll understand real-world case studies for Ceph's three interfaces, usage in OpenStack, Kubernetes, backups, and media, architectural patterns for scale and multi-tenancy, and how to do realistic cost and capacity planning. Let's get started.

#Case Study: Cloud Block Storage

#VM Disks for Cloud Platforms

Cloud providers build block storage services on top of RBD. Every VM disk is an RBD image in the volumes pool, with snapshots and clones for cloud features like disk backups and image templating. The main advantage: one pool serves thousands of VMs with safe over-provisioning thanks to thin provisioning.

ceph osd pool create volumes 256
ceph osd pool application enable volumes rbd
ceph config set global osd_pool_default_size 3

ceph osd pool application enable volumes rbd marks the pool for RBD. A three-replica scheme is the sensible default for cloud block storage that prioritizes reliability.

#Applicable Patterns

The important patterns in this case study: quota per tenant, scheduled snapshots for protection, and separate pools per tier (HDD for cheap disks, NVMe for premium disks). All three can be implemented with features you've already learned — pools, quotas, and device classes.

#Case Study: Enterprise File Services

#Shared Storage for POSIX Applications

Enterprises use CephFS to replace traditional file servers. Home directories, shared workspaces, and application backends that need POSIX semantics are mounted from a single filesystem scaled with active-active MDS.

ceph osd pool create fs_data 256
ceph osd pool create fs_meta 128
ceph fs new company-fs fs_meta fs_data

ceph fs new company-fs creates a filesystem for enterprise use. The metadata pool is made smaller but placed on fast devices, because metadata latency heavily affects file service responsiveness.

#Applicable Patterns

The important patterns: quota per department to stop one team exhausting capacity, .snap snapshots to protect files from accidental deletion, and MDS monitoring to detect metadata hot spots. All of these features were covered in episode 6.

#Case Study: S3-Compatible Object Storage

#Backups and Data Lakes

RGW is used as backup storage and data lakes. Backups are written as objects with lifecycle rules for compression and expiry, while data lakes are consumed by analytics engines. The S3-compatible nature means all existing tooling can be used right away.

aws --endpoint-url https://rgw.example.com s3api head-bucket \
  --bucket backup-prod

aws s3api head-bucket verifies the bucket can be accessed with the standard S3 protocol. From here, backup tooling like rclone or Velero can use RGW as a target without modification.

#Applicable Patterns

The important patterns: versioning to protect against overwrites, lifecycle rules to transition to cheaper storage classes, and multisite for cross-site backups. This combination of features makes RGW a serious alternative to commercial object storage.

#Ceph for OpenStack, Kubernetes, Backups, and Media

#OpenStack and Kubernetes

In OpenStack, Ceph becomes the backend for Cinder (block), Manila (shared file), and Swift (object) simultaneously — one cluster serving three services. In Kubernetes, Ceph CSI provides block volumes for databases and shared filesystems for stateless workloads. Both were covered in depth in episode 16.

#Media and Video Pipelines

For media, RGW becomes the home of large assets: raw video files, transcodes, and distribution. Multipart upload for ingestion, a CDN or cache in front for playback, and lifecycle rules to archive old productions. Media's characteristics — large files, lots of cold data — fit object storage's strengths perfectly.

#Architectural Patterns for Scale and Multi-Tenancy

#Vertical vs. Horizontal Scaling

Ceph scales horizontally: add nodes for capacity and performance. A good pattern is adding nodes in balanced groups, respecting failure domains, and not adding too many OSDs at once so rebalancing doesn't burden the cluster.

#Doing Multi-Tenancy Right

For multi-tenancy, apply the three isolation layers covered in episode 10: separate pools per tenant, different CephX keyrings, and RGW users with their own policies. Build an automated tenant provisioning template so creating new tenants is consistent and fast.

#Cost and Capacity Planning

#Calculating Effective Capacity

Effective capacity differs from raw capacity. With 3 replicas and failure tolerance, usable capacity is roughly a third of raw capacity. With erasure coding k=4, m=2, efficiency is better. Always calculate using a formula that accounts for replication and headroom:

ceph df

ceph df shows total capacity, usage, and quotas per pool. Use these numbers as the basis for capacity growth projections, not raw disk capacity.

#Total Cost Planning

Count not just hardware costs: power and cooling, network costs, labor for operations, and the cost of alternatives (cloud storage). Ceph usually wins at large scale because there are no licenses, but loses on practicality at small scale compared to managed object storage.

#Conclusion

In this episode you've seen how Ceph is used in the real world: cloud block storage case studies with RBD, enterprise file services with CephFS, and S3-compatible object storage with RGW, usage for OpenStack, Kubernetes, backups, and media, architectural patterns for scale and multi-tenancy, and how to plan cost and capacity realistically.

The key takeaways:

• RBD is the foundation of VM disks on cloud platforms with snapshots and thin provisioning.
• CephFS replaces traditional file servers with quotas and snapshots.
• RGW becomes a backup and data lake target thanks to S3 compatibility.
• One Ceph cluster serves OpenStack, Kubernetes, media, and backups at once.
• Safe multi-tenancy is achieved with isolated pools, keyrings, and users.
• Effective capacity is calculated after accounting for replication and headroom.

In the next episode, episode 21, we'll cover ecosystem & tools — the Ceph dashboard, Rook, and related open-source tools, community resources, mailing lists, and training, managed Ceph services and vendor integration, and tools for automation, provisioning, and management. Time to map the whole Ceph tool landscape!