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Cloud · head to head

Longhorn vs Prometheus

Longhorn logo

Longhorn

Cloud

Open source distributed block storage for Kubernetes, incubating at the CNCF

From
Free
Rated
-
Full reviewWebsite
Prometheus logo

Prometheus

Networking

Open source monitoring and alerting toolkit for cloud native environments

From
Free
Rated
-
Full reviewWebsite

The short version

  • Each has a real cost: Longhorn there is no vendor and no SLA, so a production incident at three in the morning is your own problem unless you buy SUSE Rancher Prime support separately.; Prometheus not suitable for per-request billing as collected data lacks 100% accuracy
  • They diverge on capability: Longhorn covers Per-volume controllers, Prometheus covers Multi-dimensional Data Model.
  • Prices and features above were last checked on 1 September 2026.

Where they differ

Only the attributes on which Longhorn and Prometheus actually diverge.

Attributes where Longhorn and Prometheus differ
AttributeLonghornPrometheus
Pricing modelOpen source, no licence feeopen-source
PlatformsLinux, KubernetesLinux, macOS, Windows
CategoryCloudNetworking
FoundedUnknown2015

Identical on both: starting price (Free), free tier (Yes), user rating (Not yet rated).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in Longhorn

  • Per-volume controllers
  • Synchronous replication
  • Snapshots and backups
  • Volume expansion
  • Disaster recovery volumes
  • Web interface

Only in Prometheus

  • Multi-dimensional Data Model
  • PromQL Query Language
  • Pull-based Collection
  • Service Discovery
  • Alerting Rules
  • Federation
  • Local Storage
  • Grafana

What people use each for

The jobs each tool is most often brought in to do.

Longhorn

  • An on-premises Kubernetes cluster with local disks and no SAN that needs replicated persistent volumesnot Prometheus
  • Edge sites where shipping a storage array is impractical and three nodes is the whole clusternot Prometheus
  • A K3s deployment where the storage layer must be light enough to run alongside the workloadsnot Prometheus
  • A team that wants snapshots and S3 backups of persistent volumes without paying per-node storage licencesnot Prometheus

Prometheus

  • Monitoring and alerting systemnot Longhorn
  • Time-series databasenot Longhorn
  • Infrastructure metrics collectionnot Longhorn

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

Longhorn

  • There is no vendor and no SLA, so a production incident at three in the morning is your own problem unless you buy SUSE Rancher Prime support separately.
  • Synchronous replication across nodes means write latency depends on the slowest replica and the network between nodes, which makes it a poor fit for latency-sensitive databases.
  • Every replica is a full copy, so three-way replication consumes three times the raw capacity, unlike erasure-coded systems that are far more space efficient.
  • It is designed for block storage on modest clusters and does not scale to the node counts or throughput that Ceph or a commercial array handles, so growth eventually forces a migration.
  • Recovery from certain degraded states, such as a volume stuck detaching or replicas failing to rebuild, requires manual intervention and knowledge of Longhorn internals that is not widely held.

Prometheus

  • Not suitable for per-request billing as collected data lacks 100% accuracy
  • Hard limit on scrape body size; large responses cause scrape failure
  • Per-scrape sample limit enforced; exceeding limit marks targets as failed
  • Not designed for long-term durable storage; optimised for metrics collection

Pricing, plan by plan

Longhorn

Free
  • LonghornFree
    • Apache 2.0 licensed, no licence fee
    • Community support via GitHub and Slack only
    • No vendor SLA or escalation path

Prometheus

Free
  • Prometheus (Open Source)Free
    • 100% open source
    • Community-driven project
    • Apache 2 License

Which should you pick?

Choose Longhorn if

  • You need per-volume controllers.
  • You want to start without paying.
  • You work on Linux, Kubernetes.
  • You also want synchronous replication.
Longhorn review

Choose Prometheus if

  • You need multi-dimensional data model.
  • You want to start without paying.
  • You work on Linux, macOS, Windows.
  • You also want promql query language.
Prometheus review

Questions people ask

Is Longhorn or Prometheus better?
Neither clearly leads. Longhorn starts at Free and Prometheus at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Longhorn or Prometheus?
Longhorn starts at Free and Prometheus at Free.
Does Longhorn or Prometheus run on more platforms?
Longhorn runs on Linux, Kubernetes. Prometheus runs on Linux, macOS, Windows.
Can I use Longhorn for free?
Both have a free tier, so you can try either at no cost before committing.
What is Longhorn best used for?
Longhorn is most often used for an on-premises kubernetes cluster with local disks and no san that needs replicated persistent volumes, edge sites where shipping a storage array is impractical and three nodes is the whole cluster, a k3s deployment where the storage layer must be light enough to run alongside the workloads, a team that wants snapshots and s3 backups of persistent volumes without paying per-node storage licences. Of those, an on-premises kubernetes cluster with local disks and no san that needs replicated persistent volumes and edge sites where shipping a storage array is impractical and three nodes is the whole cluster are not what Prometheus is typically brought in for.
What can Longhorn do that Prometheus cannot?
Longhorn covers Per-volume controllers, Synchronous replication, Snapshots and backups, Volume expansion. Prometheus covers Multi-dimensional Data Model, PromQL Query Language, Pull-based Collection, Service Discovery.

Answered from the vendors’ own pages

Longhorn: Who do we call when it breaks?

Nobody, unless you buy SUSE Rancher Prime, which includes commercial support for Longhorn. This is the decisive question for production use.

Prometheus: What does Prometheus cost?

Prometheus is completely free and open source. There are no pricing tiers or paid plans. The entire project is licensed under Apache 2 and hosted on GitHub.

Source
Longhorn: How much capacity does replication cost?

Full copies, so three replicas means three times the raw capacity. Budget accordingly rather than assuming erasure coding efficiency.

Prometheus: Is Prometheus commercial software or free?

Prometheus is 100% open source and community-driven. It is a CNCF graduated project with no commercial restrictions or licensing fees.

Source
Longhorn: Is it suitable for production databases?

For modest workloads yes, but synchronous replication adds write latency and high-transaction databases usually want something faster.

Prometheus: How is Prometheus licensed?

Prometheus is licensed under the Apache 2 License, which permits free use, modification, and distribution for commercial and non-commercial purposes.

Source
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