Grafana Mimir — Horizontally Scalable Prometheus Storage

What it is

Grafana Mimir is a horizontally scalable, highly available long-term metrics store for Prometheus and OpenTelemetry. It can handle a billion active series with multi-tenant isolation. Mimir accepts remote-write from Prometheus instances and provides a PromQL-compatible query endpoint.

Mimir targets platform teams and SREs who need to retain Prometheus metrics beyond the local retention period. It solves the problem of scaling Prometheus storage across multiple clusters, teams, and data centers.

How it saves time or tokens

Prometheus stores metrics locally with limited retention. Mimir provides unlimited retention with object storage (S3, GCS, Azure Blob) at a fraction of the cost of local SSDs. Multi-tenancy means one Mimir cluster serves multiple teams without interference. The PromQL-compatible API means existing Grafana dashboards work without modification.

How to use

1. Start Mimir in monolith mode for testing:

docker run -d --name mimir -p 9009:9009 \
  -v $(pwd)/mimir.yaml:/etc/mimir.yaml \
  grafana/mimir:latest -config.file=/etc/mimir.yaml

1. Configure Prometheus to remote-write to Mimir:

# prometheus.yml
remote_write:
  - url: http://mimir:9009/api/v1/push
    headers:
      X-Scope-OrgID: my-tenant

1. Point Grafana to Mimir as a Prometheus data source at http://mimir:9009/prometheus.

Example

# mimir.yaml - minimal configuration
target: all

common:
  storage:
    backend: filesystem
    filesystem:
      dir: /tmp/mimir-data

blocks_storage:
  backend: filesystem
  filesystem:
    dir: /tmp/mimir-blocks
  tsdb:
    dir: /tmp/mimir-tsdb

server:
  http_listen_port: 9009

multitenancy_enabled: false

Related on TokRepo

• Monitoring Tools — Observability and monitoring solutions
• DevOps Tools — Infrastructure and deployment tools

This tool integrates with standard development workflows and requires minimal configuration to get started. It is available as open-source software with documentation and community support through the official repository. The project follows semantic versioning for stable releases.

For teams evaluating this tool, the key advantage is reducing manual work in repetitive tasks. The automation provided by the built-in features means less custom code to maintain and fewer integration points to manage. This translates directly to lower maintenance costs and faster iteration cycles. The combination of cost-effective object storage, PromQL compatibility, and multi-tenant isolation makes Mimir a practical choice for organizations operating multiple Prometheus clusters that need centralized long-term metric retention.

Common pitfalls

• Monolith mode is for testing only; production deployments should use microservices mode with separate ingester, querier, and compactor components for reliability.
• Object storage configuration is critical; misconfigured bucket permissions cause silent data loss. Test write and read access before sending production metrics.
• Multi-tenancy requires setting the X-Scope-OrgID header on every request; missing headers cause writes to be rejected.