feat: k8s volumes

dump/kubernetes/README.md

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-- [Basic](./k8s.md)
+Some notes on Kubernetes.
+
+- [Some stupid basics](./stupid-basics.md)
+- [Deployment strategies](./deployment-types.md)
+- [Volumes](./volumes.md)
+- [CSI](./csi.md)
+- [CRD](./crd.md)

dump/kubernetes/crd.md

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+
+todo: add more info

dump/kubernetes/csi.md

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+## Container Storage Interface (CSI)
+
+Container Storage Interface (CSI) is an initiative to unify the storage interface of Container Orchestrator (CO) systems
+like Kubernetes, Mesos, Docker, Cloud Foundry, etc. combined with a storage vendors like Ceph, Portworx, NetApp, etc.
+
+This means, implementing a single CSI for a storage vendor is guaranteed to work with all COs.
+
+todo: add more info

dump/kubernetes/volumes.md

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+# Volumes
+
+## Requirements
+
+- Storage doesn't depend on pod lifecycle.
+- Storage must be available on all nodes
+- Storage needs to survive even if cluster crashes
+
+## Types
+
+Persistent Volume (PV)
+
+- cluster resource
+- need actual physical storage (local disk, cloud storage, etc.)
+- physical storage needs to be pre-configured, PV is just a reference to it
+- attributes are different depending on storage type
+- PV are not namespaced, they are cluster-wide
+- admin provides PV
+
+Persistent Volume Claim (PVC)
+
+- request for storage by user
+- consists of some criteria (size, access mode, etc.)
+- claim tries to find PV that matches criteria
+- PVC are namespaced
+
+We need PVC to use PV, because we don't want to know where PV is located, we just want to use it.
+
+Storage Class
+
+- SC provides dynamic provisioning of PV
+- when PVC claims storage, SC creates PV for it
+- requested in PVC, SC creates PV, PVC binds to PV
+
+## Provisioning
+
+Provisioning is the process of creating storage, it can be done statically or dynamically.
+
+Static means, that admin creates PV manually, and then user can use it.
+
+Dynamic means, that user creates PVC, and then PV is created automatically, via Storage Class.
+
+<img src="./docs/volumes.png" width="600">
+
+## Summary
+
+- Volume is a directory, possibly with some data in it, which is accessible to the containers in a pod.
+- How made available, backed by which storage medium - depends on the volume type.
+- Can't bind 2 PVC to 1 PV, but can bind 2 pods to 1 PVC.
+
+### Resources
+
+- https://www.youtube.com/watch?v=0swOh5C3OVM
+- https://www.youtube.com/watch?v=OulmwTYTauI