# Rook — Cloud-Native Storage Orchestrator for Kubernetes

> Rook turns Ceph into a first-class Kubernetes citizen by deploying, configuring, and healing distributed block, file, and object storage through an operator and a family of CRDs.

## Install

Save in your project root:

# Rook — Cloud-Native Storage Orchestrator for Kubernetes

## Quick Use
```bash
# Clone the release you want to run
git clone --single-branch --branch release-1.14 https://github.com/rook/rook.git
cd rook/deploy/examples

# Deploy the operator and a minimal Ceph cluster
kubectl apply -f crds.yaml -f common.yaml -f operator.yaml
kubectl apply -f cluster.yaml

# Create a StorageClass backed by RBD
kubectl apply -f csi/rbd/storageclass.yaml

# Watch the cluster come up
kubectl -n rook-ceph get cephcluster
```

## Introduction
Running Ceph in production used to require deep distributed-systems expertise. Rook changes that by wrapping Ceph (and historically Cassandra, NFS, YugabyteDB) in a Kubernetes operator: you declare the desired cluster in YAML, and Rook handles OSD provisioning, monitor quorum, RGW gateways, CephFS metadata servers, CSI drivers, and rolling upgrades.

## What Rook Does
- Deploys and manages a full Ceph cluster (MON, MGR, OSD, MDS, RGW) from a `CephCluster` CR.
- Provisions PersistentVolumes via RBD (block), CephFS (shared file), and S3-compatible object storage.
- Auto-heals failed OSDs, replaces disks, and rebalances placement groups without manual intervention.
- Exposes Ceph''s mirroring, erasure coding, compression, and encryption through declarative CRDs.
- Integrates with Prometheus ServiceMonitors for deep cluster-health visibility.

## Architecture Overview
Rook is a controller-runtime operator. The Rook Operator Pod watches CRs (`CephCluster`, `CephBlockPool`, `CephObjectStore`, `CephFilesystem`) and invokes the `rook` and `ceph` CLIs inside helper Pods to configure the cluster. OSDs run as one Pod per disk, co-located on the nodes that host the raw devices. CSI drivers (RBD, CephFS) mount volumes into workload Pods directly — no gateway hops.

## Self-Hosting & Configuration
- Minimum recommended footprint: 3 nodes, each with one empty raw device and 4 GiB free RAM.
- Use `useAllDevices: true` in `CephCluster` for zero-touch disk discovery, or list devices explicitly.
- Enable the dashboard with `dashboard.enabled: true` and expose via an Ingress for an operations UI.
- Tune replication/erasure with `CephBlockPool` — replicated size=3 for durability, 2+1 EC for efficiency.
- Upgrades: bump `cephVersion.image` and the operator Deployment; Rook rolls MONs and OSDs safely.

## Key Features
- Official Ceph operator — Ceph upstream recommends Rook as the Kubernetes installation method.
- Full lifecycle: install, scale, upgrade, disaster recovery (RBD mirroring, multisite RGW), deletion.
- Supports NVMe, HDD, SSD, and hybrid device classes; per-class CRUSH rules for tiered storage.
- Works on cloud (EBS, PD, Azure Disk) or on-prem bare-metal; no vendor lock-in.
- S3 multi-site, CephFS subvolumes, NFS exports, and iSCSI gateways all exposed via CRDs.

## Comparison with Similar Tools
- **OpenEBS** — multi-engine (Jiva, cStor, Mayastor, Local PV); Rook is Ceph-specific and cluster-scale heavy.
- **Longhorn** — simpler, single-engine block storage from Rancher; Rook wins for object and shared file.
- **Portworx** — commercial, feature-rich; Rook is free, open-source, and avoids vendor lock-in.
- **Piraeus / LINSTOR** — DRBD-based replication; Rook is better when you need object + file + block together.
- **StorageOS / Ondat** — closed-source stacks; Rook + Ceph gives you full auditability.

## FAQ
**Q: Can I test without real disks?**
A: Yes — use directory-based OSDs on PVCs for lab clusters; performance is limited but great for learning.

**Q: Is the non-Ceph code still maintained?**
A: No. Rook is now Ceph-only; Cassandra and NFS drivers were removed in favor of focus.

**Q: How do I monitor cluster health?**
A: Enable the Prometheus exporter in `CephCluster`; Grafana dashboards for Ceph are shipped in the repo.

**Q: Can I run it on a single node?**
A: For experiments, yes (set `mon.count: 1` and `allowMultiplePerNode: true`); production needs ≥3 nodes.

## Sources
- https://github.com/rook/rook
- https://rook.io/docs/rook/latest-release/


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Source: https://tokrepo.com/en/workflows/0085f3d4-38cf-11f1-9bc6-00163e2b0d79
Author: AI Open Source