# Ceph — Unified Distributed Storage at Scale

> Ceph is a massively scalable software-defined storage platform that presents a single cluster as block, object, and file storage, powering private clouds and petabyte-scale backups.

## Install

Save as a script file and run:

# Ceph — Unified Distributed Storage at Scale

## Quick Use
```bash
# Bootstrap a single-node cluster with cephadm
curl --silent --remote-name --location https://github.com/ceph/ceph/raw/main/src/cephadm/cephadm
chmod +x cephadm
./cephadm add-repo --release reef
./cephadm install
cephadm bootstrap --mon-ip 192.168.1.10

# Create a pool and map an RBD image
ceph osd pool create rbd 32
rbd create demo --size 1G --pool rbd
rbd map demo -p rbd
mkfs.ext4 /dev/rbd0 && mount /dev/rbd0 /mnt/demo
```

## Introduction
Ceph is the reference open-source distributed storage system, originally developed at UC Santa Cruz and now stewarded by the Ceph Foundation (Linux Foundation). It powers OpenStack, Rook on Kubernetes, and thousands of private clouds.

## What Ceph Does
- Serves RBD block devices for VMs and databases
- Exposes S3/Swift-compatible object storage via RGW
- Provides POSIX file access via CephFS with snapshots
- Self-heals data by replicating or erasure-coding placement groups
- Scales from three nodes to exabytes with no single point of failure

## Architecture Overview
A Ceph cluster is built from MON daemons (cluster membership), MGR daemons (metrics/orchestration), OSDs (one per disk, the actual storage), MDS (for CephFS), and RGW (for S3). Data is sharded into placement groups and mapped to OSDs via CRUSH, a pseudo-random distribution algorithm.

## Self-Hosting & Configuration
- Use `cephadm` (containerized) or Rook for Kubernetes-native installs
- Minimum 3 MONs and 3 hosts for production
- NVMe for WAL/DB, spinning disks for bulk OSDs is a typical mix
- Tune CRUSH rules to respect failure domains (rack, host, row)
- Enable the dashboard MGR module for a web UI on port 8443

## Key Features
- Three storage interfaces from one cluster
- Erasure coding saves 30–60 percent vs replication
- RBD mirroring and RGW multisite for DR
- Rolling upgrades with zero downtime
- Integrates natively with OpenStack, Proxmox, and Kubernetes via Rook

## Comparison with Similar Tools
- **MinIO** — S3 only, simpler, single-tier
- **GlusterFS** — file focused, smaller communities, less active
- **Longhorn** — block only, Kubernetes-scoped, lighter
- **OpenEBS** — container-attached storage, not a unified cluster
- **SeaweedFS** — object/file focused, extreme small-file performance

## FAQ
**Q:** How many nodes do I need?
A: Three is the production minimum; one-node labs work with `osd_crush_chooseleaf_type=0`.

**Q:** Do I need dedicated networks?
A: Recommended — separate public and cluster networks ≥ 10 GbE for healthy recovery.

**Q:** Is Rook a fork?
A: No, Rook is a Kubernetes operator that deploys upstream Ceph.

**Q:** Can Ceph replace my SAN?
A: Yes for most block workloads, provided the network and disks are sized correctly.

## Sources
- https://github.com/ceph/ceph
- https://docs.ceph.com/

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Source: https://tokrepo.com/en/workflows/609469f1-38fa-11f1-9bc6-00163e2b0d79
Author: Script Depot