kube/longhorn-system/README.md

# Longhorn distributed block storage system

## For users

You should really avoid using Longhorn as it has over time
[proven to be unreliable system](https://www.reddit.com/r/kubernetes/comments/1cbggo8/longhorn_is_unreliable/).
Prefer using remote databases in your application via
the Kubernetes operator pattern.

Use Longhorn for applications that need persistent storage, but are unable
to provide replication in the application layer:

* Applications that insist writing into filesystem
* Applications that serve Git repositories (eg Gitea)
* Applications that check out Git repositories (eg Woodpecker, Drone and CI systems)
* Applications that need to use SQLite

Instead of using built-in `longhorn` storage class, please add new storage class
with suitable replication, data locality parameters and reclaim policy
[here](https://git.k-space.ee/k-space/kube/src/branch/master/storage-class.yaml)

Longhorn backups are made once per day and it's configured to be uploaded to
the Minio S3 bucket hosted at nas.k-space.ee


## For administrators

Longhorn was last upgraded with following snippet:

```
wget https://raw.githubusercontent.com/longhorn/longhorn/v1.6.2/deploy/longhorn.yaml
patch -p0 < changes.diff
kubectl -n longhorn-system apply -f longhorn.yml -f application-extras.yml -f backup.yaml
```

After initial deployment `dedicated=storage:NoSchedule` was specified
for `Kubernetes Taint Toleration` under `Setting -> General` on
[Longhorn Dashboard](https://longhorn.k-space.ee/).
Suitable nodes were tagged with  `storage` and Longhorn scheduling was disabled on others.
This is to prevent scheduling Longhorn data on arbitrary Kubernetes nodes as
`storage[1-4].kube.k-space.ee` nodes are the ones which have additional 200G volume mounted at `/mnt/persistent/`