Kubernetes CSI

Kubernetes CSI
Name	Kubernetes CSI
Developer	The Linux Foundation
Initial release	2017
Operating system	Cross-platform
License	Apache License 2.0

Kubernetes CSI

Kubernetes CSI is a cloud-native storage interface standard for container orchestration, designed to enable external storage vendors and projects to expose block and file storage to Kubernetes clusters. It provides a pluggable model so projects like Rook (software), OpenEBS, Ceph, Portworx, and vendors such as VMware, NetApp, Pure Storage can implement storage functionality without modifying the core Kubernetes incubator codebase. CSI unifies storage integration across cloud providers like Amazon Web Services, Google Cloud Platform, Microsoft Azure, and on-premises environments managed by Red Hat, SUSE, and Canonical.

Overview

CSI was developed through collaboration between The Linux Foundation, the Cloud Native Computing Foundation, and major vendors including Google, IBM, Amazon (company), Microsoft Corporation, and VMware, Inc.. The project emerged from discussions at KubeCon conferences and working groups within the CNCF. CSI standardizes the plugin model originally implemented as in-tree volume plugins in Kubernetes to enable independent lifecycle, versioning, and distribution by storage vendors such as Dell Technologies, Hitachi Vantara, Huawei, and NetApp. Key motivations include portability across Linux distributions, compatibility with orchestration systems used in enterprises like Red Hat OpenShift, and support for modern features pioneered by communities around Ceph, GlusterFS, and iSCSI ecosystems.

Architecture

CSI defines a set of gRPC APIs and a driver model implemented by storage providers such as Rook (software), Longhorn (software), Portworx, and OpenEBS. The architecture separates concerns between control plane components in Kubernetes control plane and node-level components running on kubelet hosts. CSI introduces sidecar containers managed by controllers like the CSI external-provisioner, CSI external-attacher, and CSI external-resizer to integrate with controllers from projects such as Prometheus, CoreDNS, and etcd. Interaction with cloud provider services like Amazon EBS, Google Persistent Disk, and Azure Disk is coordinated through CSI drivers and Container Storage Interface specifications, enabling features like volume snapshot and volume cloning supported by projects including Velero and Stash (software).

CSI Drivers

CSI drivers implement RPCs defined by the CSI specification and are maintained by vendors and communities such as NetApp, Pure Storage, Dell EMC, VMware, Inc., IBM, Hitachi Vantara, and open-source projects like Ceph, GlusterFS, Longhorn (software), Rook (software), OpenEBS, and Topolvm. Drivers provide capabilities including dynamic provisioning, offline and online resizing, snapshots, cloning, and topology-aware provisioning compatible with orchestration extensions from Kubernetes SIG Storage, SIG Node, and SIG API Machinery. Many drivers expose additional monitoring and metrics compatible with Prometheus exporters and integrate with logging stacks using Fluentd, Logstash, or Elasticsearch deployments.

Installation and Deployment

CSI drivers are deployed as Kubernetes workloads using manifests, Helm charts, and operators authored by groups such as Operator Framework, Helm, and vendors including Red Hat and Canonical. Typical deployments include a controller deployment in the kube-system namespace, daemonsets on each node, and RBAC resources compatible with Kubernetes API Server configurations. Tools for deployment and lifecycle management include Helm, Kustomize, and operators developed with Operator SDK and frameworks like Kubebuilder. Cloud providers distribute managed drivers through marketplaces and integrations with Google Kubernetes Engine, Amazon Elastic Kubernetes Service, and Azure Kubernetes Service.

API and CRDs

CSI exposes functionality through standardized gRPC APIs defined by the Container Storage Interface working group and maps volume lifecycle to Kubernetes PersistentVolume (PV), PersistentVolumeClaim (PVC), and StorageClass resources. Extensions and value-added features are often surfaced via CustomResourceDefinitions (CRDs) created by projects such as Rook (software), OpenEBS, Longhorn (software), and Portworx, enabling constructs like VolumeSnapshot and VolumeSnapshotClass which interact with snapshot controllers maintained by SIG Storage. CSI also integrates with admission controllers and APIs managed by kube-apiserver and can be observed via metrics compatible with Prometheus and tracing systems such as Jaeger.

Lifecycle and Operations

Operational tasks for CSI include driver upgrades, backup and restore, scaling, and troubleshooting using logs and metrics tools like Prometheus, Grafana, Fluentd, and ELK Stack. Lifecycle management is often implemented via operators from Red Hat, Rook (software), or vendor-specific controllers enabling automation for tasks tied to Kubernetes Cluster API flows, rolling upgrades coordinated with kubelet and kube-proxy, and compatibility testing with conformance suites produced by CNCF and SIG Storage. Troubleshooting relies on components such as the CSI node plugin, controller plugin, and sidecars, and integrates with incident response processes used by enterprises like Netflix, Airbnb, and Spotify running stateful workloads.

Security and Access Control

CSI drivers must operate within Kubernetes security constructs including Role-Based Access Control, PodSecurityPolicy predecessors, and newer constructs like Pod Security Admission and OPA Gatekeeper. Secrets for backend access are commonly managed through integrations with Kubernetes Secrets, external secret managers such as HashiCorp Vault, and cloud IAM systems from Amazon Web Services, Google Cloud Platform, and Microsoft Azure. Network-level controls are achieved using projects like Calico, Weave Net, and Istio alongside storage-specific encryption options from vendors including NetApp and Pure Storage. Compliance and auditing often reference standards maintained by organizations such as NIST and ISO, while supply-chain security leverages initiatives like sigstore and Notary (project).

Category:Kubernetes