Longhorn

Longhorn is a distributed block storage system for Kubernetes. Longhorn is cloud-native storage built using Kubernetes and container primitives.

Their Helm-Chart is available at: https://github.com/longhorn/charts

Installation

Longhorn is included with ClusterTool. It rolls out a, default, storageClass named longhorn, that saves its data on the systemdisk.

Issues with Longhorn and Volsync

Volsync creates backup each day and uses snapshots to do so. This leads to a lot of snapshot creations which will be deleted after the backup is done.

Longhorn wont free/trim the space gained by the deletion of the snapshots and will keep it as used. This can lead to a no-disk-space error after some time depending on the amount of volsync backups and their size. This can be prevented by adding the following ReccuringTask to Longhorn:

apiVersion: longhorn.io/v1beta2
kind: RecurringJob
metadata:
  name: trim
  namespace: longhorn-system
spec:
  concurrency: 1
  cron: 0 0 * * *
  groups:
  - default
  name: trim
  retain: 0
  task: filesystem-trim

This runs a filesystem trim at midnight UTC. To free the “used” space.

In addition to trim, it is possible to delete and cleanup all snapshots by adding tasks for snapshot-delete and snapshot-cleanup.

apiVersion: longhorn.io/v1beta2
kind: RecurringJob
metadata:
  name: delete
  namespace: longhorn-system
spec:
  concurrency: 1
  cron: 00 22 * * *
  groups:
  - default
  name: delete
  retain: 0
  task: snapshot-delete

This runs a snapshot delete task at 22:00 UTC.

apiVersion: longhorn.io/v1beta2
kind: RecurringJob
metadata:
  name: cleanup
  namespace: longhorn-system
spec:
  concurrency: 1
  cron: 30 22 * * *
  groups:
  - default
  name: cleanup
  retain: 0
  task: snapshot-cleanup

This runs a snapshot cleanup task at 22:30 UTC.

Other references

https://longhorn.io/docs/1.8.0/deploy/install/install-with-helm
https://volsync.readthedocs.io/en/latest/installation/index.html
https://longhorn.io/docs/1.8.0/snapshots-and-backups/scheduling-backups-and-snapshots/#using-the-manifest