Longhorn vs Rook-Ceph: Kubernetes Storage Compared

Every Kubernetes cluster eventually needs persistent storage. The question is: which solution?

For self-hosted clusters without cloud provider storage classes, two options dominate: Longhorn and Rook-Ceph. Both are CNCF projects. Both provide replicated block storage. Both work well.

But they’re very different in philosophy, complexity, and use cases. I’ve run both in production. Let me share what I’ve learned.

The Fundamental Difference

Longhorn: Simple distributed block storage built for Kubernetes. Each volume is replicated across nodes using standard Linux storage primitives.

Rook-Ceph: Kubernetes operator for Ceph, a battle-tested distributed storage system that predates Kubernetes by years. Brings Ceph’s full feature set into Kubernetes.

The trade-off:

Longhorn prioritizes simplicity
Rook-Ceph prioritizes features and scale

Longhorn: The Simple Choice

flowchart TD
    subgraph longhorn["Longhorn Architecture"]
        subgraph node1["Node 1"]
            E1["Longhorn Engine"]
            R1["Replica"]
        end
        subgraph node2["Node 2"]
            E2["Longhorn Engine"]
            R2["Replica"]
        end
        subgraph node3["Node 3"]
            R3["Replica"]
        end
    end

    PV["PersistentVolume"] --> E1
    E1 --> R1
    E1 --> R2
    E1 --> R3

How Longhorn Works

Engine per volume: Each PVC gets a dedicated Longhorn engine (runs as a pod)
Replicas on nodes: Data replicated to multiple nodes’ local disks
Synchronous replication: All replicas written before acknowledging
iSCSI frontend: Engine exposes volume via iSCSI to the workload

Installing Longhorn

helm repo add longhorn https://charts.longhorn.io
helm repo update

helm install longhorn longhorn/longhorn \
  --namespace longhorn-system \
  --create-namespace

Basic configuration:

# longhorn-values.yaml
defaultSettings:
  defaultReplicaCount: 3
  defaultDataPath: /var/lib/longhorn
  storageMinimalAvailablePercentage: 15
  defaultLonghornStaticStorageClass: longhorn

persistence:
  defaultClass: true
  defaultClassReplicaCount: 3

Longhorn Strengths

Simplicity: Install with Helm, get storage. No dedicated storage nodes, no complex configuration.

UI: Built-in web interface for volume management, backup status, node health.

Backup: Native backup to S3-compatible storage with incremental snapshots.

Kubernetes-native: Designed for Kubernetes from the start. No legacy baggage.

Longhorn Limitations

Performance: Good for most workloads, but not optimized for extreme IOPS. Each volume runs through its own engine pod.

Scale: Works well up to ~100 nodes. Beyond that, consider alternatives.

Storage efficiency: Each replica is a full copy. No erasure coding.

Rook-Ceph: The Feature-Rich Choice

flowchart TD
    subgraph rook["Rook-Ceph Architecture"]
        subgraph mgmt["Management"]
            OP["Rook Operator"]
            MON["Ceph Monitors"]
            MGR["Ceph Manager"]
        end
        subgraph storage["Storage"]
            OSD1["OSD<br/>(disk 1)"]
            OSD2["OSD<br/>(disk 2)"]
            OSD3["OSD<br/>(disk 3)"]
            OSD4["OSD<br/>(disk 4)"]
        end
        subgraph access["Access"]
            RBD["RBD<br/>(Block)"]
            RGW["RGW<br/>(Object)"]
            CFS["CephFS<br/>(Filesystem)"]
        end
    end

    PV["PersistentVolume"] --> RBD
    RBD --> OSD1
    RBD --> OSD2

How Rook-Ceph Works

OSDs on disks: Each disk becomes an Object Storage Daemon
CRUSH algorithm: Data distributed across OSDs using placement rules
Multiple access methods: Block (RBD), Object (S3-compatible), Filesystem (CephFS)
Monitors for consensus: Cluster state managed by monitor daemons

Installing Rook-Ceph

helm repo add rook-release https://charts.rook.io/release
helm repo update

# Install Rook operator
helm install rook-ceph rook-release/rook-ceph \
  --namespace rook-ceph \
  --create-namespace

# Create Ceph cluster
kubectl apply -f ceph-cluster.yaml

Cluster configuration:

# ceph-cluster.yaml
apiVersion: ceph.rook.io/v1
kind: CephCluster
metadata:
  name: rook-ceph
  namespace: rook-ceph
spec:
  cephVersion:
    image: quay.io/ceph/ceph:v18.2.0

  mon:
    count: 3
    allowMultiplePerNode: false

  mgr:
    count: 2

  storage:
    useAllNodes: true
    useAllDevices: false
    deviceFilter: "^sd[b-z]"  # Use sdb, sdc, etc.

  resources:
    mon:
      requests:
        cpu: 500m
        memory: 1Gi
    osd:
      requests:
        cpu: 500m
        memory: 2Gi

Rook-Ceph Strengths

Scale: Handles petabytes. Used by CERN, Bloomberg, and other massive deployments.

Features: Block, object, and filesystem storage. Erasure coding. Snapshots. Mirroring.

Performance tuning: Extensive options for optimization. Can be tuned for specific workloads.

Storage efficiency: Erasure coding reduces overhead (e.g., 1.5x instead of 3x for replication).

Rook-Ceph Limitations

Complexity: More moving parts. Monitors, managers, OSDs all need resources and attention.

Resource overhead: Minimum 3 monitors, 2 managers, plus OSDs. Significant memory usage.

Learning curve: Ceph has decades of features and configuration options.

Dedicated storage nodes: For performance, often need dedicated nodes for OSDs.

Head-to-Head Comparison

Aspect	Longhorn	Rook-Ceph
Complexity	Low	High
Setup time	10 minutes	30+ minutes
Resource overhead	Low	High
Max scale	~100 nodes	1000+ nodes
Storage types	Block only	Block, Object, Filesystem
Performance	Good	Excellent (when tuned)
Storage efficiency	3x (replication)	1.5x+ (erasure coding)
Backup	Built-in S3	External tools
UI	Excellent	Ceph Dashboard
Community	Growing	Mature

When to Choose Longhorn

Choose Longhorn when:

Small to medium clusters (under 100 nodes)
Simplicity matters — You want storage that “just works”
Limited ops capacity — Small team, can’t dedicate time to storage management
General workloads — Databases, stateful apps with moderate I/O
Homelab or edge — Resource-constrained environments

# Typical Longhorn workload
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: postgres-data
spec:
  accessModes:
    - ReadWriteOnce
  storageClassName: longhorn
  resources:
    requests:
      storage: 100Gi

When to Choose Rook-Ceph

Choose Rook-Ceph when:

Large clusters (100+ nodes)
Multiple storage types needed — Block AND object AND filesystem
Performance critical — Need to tune for specific workloads
Storage efficiency matters — Erasure coding reduces costs
Dedicated storage team — People who can learn and operate Ceph

# Rook-Ceph with erasure coding
apiVersion: ceph.rook.io/v1
kind: CephBlockPool
metadata:
  name: replicated-pool
  namespace: rook-ceph
spec:
  failureDomain: host
  replicated:
    size: 3
---
apiVersion: ceph.rook.io/v1
kind: CephBlockPool
metadata:
  name: erasure-coded-pool
  namespace: rook-ceph
spec:
  failureDomain: host
  erasureCoded:
    dataChunks: 2
    codingChunks: 1

Performance Considerations

Longhorn Performance

# Tune replica count for performance vs durability
defaultSettings:
  defaultReplicaCount: 2  # Faster than 3, less durable

# Use dedicated disk path
defaultDataPath: /mnt/fast-ssd/longhorn

Longhorn is I/O bound by the engine pod. For high IOPS workloads, it may bottleneck.

Rook-Ceph Performance

# Dedicated OSD nodes
spec:
  placement:
    osd:
      nodeAffinity:
        requiredDuringSchedulingIgnoredDuringExecution:
          nodeSelectorTerms:
            - matchExpressions:
                - key: storage-node
                  operator: In
                  values:
                    - "true"

# NVMe optimization
storage:
  config:
    osdsPerDevice: "1"
    storeType: bluestore

Ceph can saturate modern NVMe drives when properly configured.

Backup Strategies

Longhorn Backup

Built-in, configure S3 target:

defaultSettings:
  backupTarget: s3://longhorn-backups@us-east-1/
  backupTargetCredentialSecret: longhorn-s3-credentials

Schedule backups per volume:

apiVersion: longhorn.io/v1beta1
kind: RecurringJob
metadata:
  name: daily-backup
spec:
  cron: "0 2 * * *"
  task: backup
  groups:
    - default
  retain: 7

Rook-Ceph Backup

Use Velero with Ceph CSI snapshots:

velero install \
  --provider aws \
  --plugins velero/velero-plugin-for-csi \
  --features=EnableCSI

Or native Ceph mirroring for disaster recovery between clusters.

My Setup

I run Longhorn in my homelab:

# My Longhorn configuration
defaultSettings:
  defaultReplicaCount: 2  # 3 nodes, 2 replicas
  defaultDataPath: /mnt/storage/longhorn
  backupTarget: s3://backups@minio/longhorn/
  backupTargetCredentialSecret: minio-credentials
  storageMinimalAvailablePercentage: 20

persistence:
  defaultClass: true

Why Longhorn?

3 nodes — Too small for Ceph overhead
Simplicity — I don’t want to debug Ceph at 2 AM
Backup integration — S3 backups to my MinIO
Resource efficiency — Every MB matters on small nodes

If I were running 50+ nodes or needed object storage, I’d switch to Ceph.

Migration Path

Starting with Longhorn and growing? You can migrate:

Backup data from Longhorn volume
Deploy Rook-Ceph alongside
Restore to Ceph volumes
Update workloads to use new StorageClass
Retire Longhorn once migrated

Both support CSI, so the interface to workloads is identical.

Why This Matters

Storage is the hardest part of Kubernetes. Get it wrong and you lose data. Over-engineer it and you waste resources maintaining complexity you don’t need.

The right choice depends on your scale:

Homelab/small clusters: Longhorn
Medium production: Either, based on features needed
Large scale: Rook-Ceph

Both are solid. Both will serve you well. The difference is how much complexity you’re willing to manage.

Simple systems fail in simple ways. Complex systems fail in complex ways. Choose the complexity you can handle.

The Fundamental Difference#

Longhorn: The Simple Choice#

How Longhorn Works#

Installing Longhorn#

Longhorn Strengths#

Longhorn Limitations#

Rook-Ceph: The Feature-Rich Choice#

How Rook-Ceph Works#

Installing Rook-Ceph#

Rook-Ceph Strengths#

Rook-Ceph Limitations#

Head-to-Head Comparison#

When to Choose Longhorn#

When to Choose Rook-Ceph#

Performance Considerations#

Longhorn Performance#

Rook-Ceph Performance#

Backup Strategies#

Longhorn Backup#

Rook-Ceph Backup#

My Setup#

Migration Path#

Why This Matters#