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Cake day: 2023年7月8日

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  • There is a lot of complexity and overhead involved in either system. But, the benefits of containerizing and using Kubernetes allow you to standardize a lot of other things with your applications. With Kubernetes, you can standardize your central logging, network monitoring, and much more. And from the developers perspective, they usually don’t even want to deal with VMs. You can run something Docker Desktop or Rancher Desktop on the developer system and that allows them to dev against a real, compliant k8s distro. Kubernetes is also explicitly declarative, something that OpenStack was having trouble being.

    So there are two swim lanes, as I see it: places that need to use VMs because they are using commercial software, which may or may not explicitly support OpenStack, and companies trying to support developers in which case the developers probably want a system that affords a faster path to production while meeting compliance requirements. OpenStack offered a path towards that later case, but Kubernetes came in and created an even better path.

    PS: I didn’t really answer your question”capable” question though. Technically, you can run a kubernetes cluster on top of OpenStack, so by definition Kubernetes offers a subset of the capabilities of OpenStack. But, it encapsulates the best subset for deploying and managing modern applications. Go look at some demos of ArgoCD, for example. Go look at Cilium and Tetragon for network and workload monitoring. Look at what Grafana and Loki are doing for logging/monitoring/instrumentation.

    Because OpenStack lets you deploy nearly anything (and believe me, I was slinging OVAs for anything back in the day) you will never get to that level of standardization of workloads that allows you to do those kind of things. By limiting what the platform can do, you can build really robust tooling around the things you need to do.





  • You’re on the right track here. Longhorn kind of makes RAID irrelevant, but only for data stored in Longhorn. So anything on the host disk and not a PV is at risk. I tend to use MicroOS and k3s, so I’m okay with the risk, but it’s worth considering.

    For replicas, I wouldn’t jump straight to 3 and ignore 2. A lot of distributed storage systems use 3 so that they can resolve the “split brain” problem. Basically, if half the nodes can’t talk to each other, the side with quorum (2 of 3) knows that it can keep going while the side with 1 of 3 knows to stop accepting writes it can’t replicate. But Longhorn already does this in a Kubernetes native way. So it can get away with replica 2 because only one of the replicas will get the lease from the kube-api.


  • Longhorn is basically just acting like a fancy NFS mount in this configuration. It’s a really fancy NFS mount that will work well with kubernetes, for things like PVC resizing and snapshots, but longhorn isn’t really stretching its legs in this scenario.

    I’d say leave it, because it’s already setup. And someday you might add more (non-RAID) disks to those other nodes, in which case you can set Longhorn to replicas=2 and get some better availability.