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...you're essentially turning the host OS into both a resource manager and isolation boundary enforcer, which is... kind of what hypervisors were specifically d
by neom 2y ago
...you're essentially turning the host OS into both a resource manager and isolation boundary enforcer, which is... kind of what hypervisors were specifically designed to do, just at a different level. When the container companies were all starting to come out, I never thought it was a good idea, given what I was building I never said anything because "of course the VM guy would not like containers" - I thought many times about what an ISO+VM "container" product would look like but at the time it would have been hard to match the performance of containers even if we could have gotten the developer experience super good. VM: Cold start: ~10 seconds with an optimized ISO, Management overhead: ~256MB baseline, Consistent performance profile. K8s: Cold start, ~30-50 seconds (control plane decisions + networking setup), management overhead: 1-2GB for the control plane alone, more variable performance due to overlay networking.
imo real question is: at what scale/complexity does k8 overhead get amortized by its management benefits? For a number of services, I suspect it never does. I will dutifully accept all my downvotes now.
- openquery 2y agoI haven't played around with hypervisors much but the whole point of k8s is not just isolation but all the primitives the control plane gives you which you don't need to implement. Things like StatefulSet, ReplicaSet, Volumes, HorizontalPodAutoscaler, Service, DNS, ConfigMaps, Secrets, Accounts, Roles, Permissions etc. Also the container runtime which is containerd by default I believe can be switched out for micro vms like Firecracker (never done this though - not sure how painful it is).
- mdaniel 2y agoOr even the other direction, upward toward full vms, or hybrid: https://github.com/kubevirt/kubevirt/blob/v1.4.0/docs/architecture-simple.png https://github.com/kubevirt/kubevirt/blob/v1.4.0/docs/archit...