Longhorn – A Kubernetes-Native Filesystem

Summary

The other day, I took a look at Longhorn again. I briefly looked at it earlier, as a way to get volumes that are writeable from more than one node. I tossed it away then, because I mistook it for nothing more than a glorified NFS server. I was quite wrong. At the time of writing, I already know I’m going to make fundamental changes, I will not run with a 2-node cluster permanently, because the latency I have isn’t necessarily a good idea. However, longhorn will play a vital play in my DR strategy. I wanted to play with longhorn in a multi-node cluster before going there, though, because when I create my proper DR strategy, my 2nd node will be occupied with being a cluster in its own. Features of Longhorn Longhorn in a way has many similarities with ZFS, but made for a distributed environment like Kubernetes. In a nutshell, Longhorn provision block devices out of a pool – or several, I have an SSD pool and a HDD pool. You’ll create storage classes using those pools, with the properties you like. A storageclass is sort of a template for a volume, that says what properties it should have when it’s created. You can still change it afterwards, though. Longhorn also comes with a decent web console, making it easy to get overview of – and manage – your Longhorn storage solution. It has built-in support for snapshot-based backups, most commonly to S3 (or compatible) buckets. First, you need to decide how/if you want to replicate volumes. For the sake of experimenting with Longhorn, I have been running more like a two-node system for a while, though the latency between my on-prem and cloud makes it not so ideal. I’ll probably end up doing something different, a separate DR cluster, but more of that in another blog post. I have chosen two replicas. Longhorn does master/slave replication only, but it is easy to promote a replica to master, and most often it happens automatically when a POD wants to mount it on one of the nodes. Installing longhorn I provision my longhorn throu...