Originally reported by Container Journal. Original announcement date: June 2020.
What Is Longhorn?
Longhorn is open-source, cloud-native block storage software originally developed by Rancher Labs. At the time of its general availability announcement, it had been accepted as a sandbox project under the Cloud Native Computing Foundation (CNCF), placing it alongside other foundational Kubernetes ecosystem projects.
Rancher Labs announced general availability of Longhorn to give Kubernetes clusters reliable, production-grade access to persistent block storage — a long-standing pain point for teams running stateful, distributed applications on Kubernetes.
Why Persistent Storage on Kubernetes Is Hard
Kubernetes was originally designed with stateless workloads in mind. Stateful applications — databases, message queues, content management systems — require persistent volumes that survive pod restarts and node failures. Traditional storage solutions were not designed with Kubernetes orchestration in mind, creating operational gaps around provisioning, replication, snapshots, and disaster recovery.
Longhorn addresses these gaps natively within the Kubernetes control plane, rather than bolting on external storage management tooling.
Key Features of Longhorn
- One-click persistent storage: Volumes can be added to a Kubernetes cluster through a single UI action, lowering the barrier for teams unfamiliar with storage administration.
- Snapshots and backup/restore: Built-in snapshot capabilities allow point-in-time recovery. Backup and restore supports recovery time and recovery point objectives (RTO/RPO) across clusters.
- Asynchronous cross-cluster replication: IT teams can schedule asynchronous replication between Longhorn instances running on separate clusters, supporting disaster recovery workflows.
- Thin provisioning: Storage is allocated on demand rather than pre-allocated, improving resource utilization.
- Non-disruptive volume expansion: Volumes can be resized without taking workloads offline.
- Standalone UI and CLI: Longhorn ships with its own web-based dashboard as well as CLI integration with standard Kubernetes tooling (
kubectl). - Live upgrades: Longhorn can be upgraded without downtime to running workloads.
Architecture: Lightweight and Microservices-Based
Longhorn is implemented in approximately 30,000 lines of Go code. Its relatively small footprint compared with legacy storage software comes from building directly on existing Linux storage primitives rather than reimplementing low-level storage logic from scratch.
Each Longhorn volume is managed by its own dedicated micro-controller — a microservices architecture that isolates fault domains. A failure in one volume controller does not cascade to other volumes, improving overall cluster resilience.
This design also enables Longhorn to act as a bridge layer to existing enterprise storage infrastructure. It can be deployed on top of:
- NFS storage arrays
- iSCSI storage arrays
- Fibre Channel storage arrays
- Cloud-provider block storage systems
This means organizations that have invested in enterprise storage hardware can integrate it with Kubernetes workloads through Longhorn without abandoning existing infrastructure.
Commercial Support and Rancher Integration
Alongside the open-source CNCF project, Rancher Labs (now part of SUSE) offered commercial support for Longhorn to customers using its Rancher Kubernetes distribution. This gave enterprise teams a supported path to production use, including SLA-backed assistance for storage issues on Rancher-managed clusters.
The Broader Context: Kubernetes Storage Maturity
The announcement reflected a maturing Kubernetes ecosystem where storage was becoming a first-class concern. At the time, CNCF survey data suggested that while a minority of respondents were running storage projects in production, a significant portion were evaluating them — indicating growing enterprise intent to solve persistent storage at the platform level.
The trajectory points toward storage management converging with Kubernetes cluster operations. Rather than storage administrators managing arrays independently from application teams, persistent volume lifecycle — provisioning, snapshotting, replication, and recovery — is increasingly managed through Kubernetes-native APIs and controllers like Longhorn.
External, dedicated storage arrays will continue to exist for high-volume, specialized workloads. However, for primary workload storage tightly coupled to containerized applications, cloud-native solutions like Longhorn reduce operational overhead and total cost compared with traditional storage platforms.
Getting Started with Longhorn
Longhorn can be installed on any Kubernetes cluster using Helm, kubectl manifests, or directly from the Rancher Apps catalog. The official project documentation is maintained at longhorn.io and the source code is available on GitHub.
# Install Longhorn via Helm
helm repo add longhorn https://charts.longhorn.io
helm repo update
helm install longhorn longhorn/longhorn \
--namespace longhorn-system \
--create-namespaceCode language: PHP (php)After installation, the Longhorn UI is accessible via a Kubernetes service, and storage classes are automatically created and available to any workload requesting persistent volume claims.