Wednesday, January 10, 2018
Introducing Container Storage Interface (CSI) Alpha for Kubernetes
One of the key differentiators for Kubernetes has been a powerful volume plugin system that enables many different types of storage systems to:
- Automatically create storage when required.
- Make storage available to containers wherever they’re scheduled.
- Automatically delete the storage when no longer needed.
Adding support for new storage systems to Kubernetes, however, has been challenging.
Kubernetes 1.9 introduces an alpha implementation of the Container Storage Interface (CSI) which makes installing new volume plugins as easy as deploying a pod. It also enables third-party storage providers to develop solutions without the need to add to the core Kubernetes codebase.
Because the feature is alpha in 1.9, it must be explicitly enabled. Alpha features are not recommended for production usage, but are a good indication of the direction the project is headed (in this case, towards a more extensible and standards based Kubernetes storage ecosystem).
Why Kubernetes CSI?
Kubernetes volume plugins are currently “in-tree”, meaning they’re linked, compiled, built, and shipped with the core kubernetes binaries. Adding support for a new storage system to Kubernetes (a volume plugin) requires checking code into the core Kubernetes repository. But aligning with the Kubernetes release process is painful for many plugin developers.
The existing Flex Volume plugin attempted to address this pain by exposing an exec based API for external volume plugins. Although it enables third party storage vendors to write drivers out-of-tree, in order to deploy the third party driver files it requires access to the root filesystem of node and master machines.
In addition to being difficult to deploy, Flex did not address the pain of plugin dependencies: Volume plugins tend to have many external requirements (on mount and filesystem tools, for example). These dependencies are assumed to be available on the underlying host OS which is often not the case (and installing them requires access to the root filesystem of node machine).
CSI addresses all of these issues by enabling storage plugins to be developed out-of-tree, containerized, deployed via standard Kubernetes primitives, and consumed through the Kubernetes storage primitives users know and love (PersistentVolumeClaims, PersistentVolumes, StorageClasses).
What is CSI?
The goal of CSI is to establish a standardized mechanism for Container Orchestration Systems (COs) to expose arbitrary storage systems to their containerized workloads. The CSI specification emerged from cooperation between community members from various Container Orchestration Systems (COs)–including Kubernetes, Mesos, Docker, and Cloud Foundry. The specification is developed, independent of Kubernetes, and maintained at https://github.com/container-storage-interface/spec/blob/master/spec.md.
Kubernetes v1.9 exposes an alpha implementation of the CSI specification enabling CSI compatible volume drivers to be deployed on Kubernetes and consumed by Kubernetes workloads.
How do I deploy a CSI driver on a Kubernetes Cluster?
CSI plugin authors will provide their own instructions for deploying their plugin on Kubernetes.
How do I use a CSI Volume?
Assuming a CSI storage plugin is already deployed on your cluster, you can use it through the familiar Kubernetes storage primitives: PersistentVolumeClaims, PersistentVolumes, and StorageClasses.
CSI is an alpha feature in Kubernetes v1.9. To enable it, set the following flags:
CSI is an alpha feature in Kubernetes v1.9. To enable it, set the following flags:
API server binary:
--feature-gates=CSIPersistentVolume=true
--runtime-config=storage.k8s.io/v1alpha1=true
API server binary and kubelet binaries:
--feature-gates=MountPropagation=true
--allow-privileged=true
Dynamic Provisioning
You can enable automatic creation/deletion of volumes for CSI Storage plugins that support dynamic provisioning by creating a StorageClass pointing to the CSI plugin.
The following StorageClass, for example, enables dynamic creation of “fast-storage” volumes by a CSI volume plugin called “com.example.team/csi-driver”.
kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
name: fast-storage
provisioner: com.example.team/csi-driver
parameters:
type: pd-ssd
To trigger dynamic provisioning, create a PersistentVolumeClaim object. The following PersistentVolumeClaim, for example, triggers dynamic provisioning using the StorageClass above.
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: my-request-for-storage
spec:
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 5Gi
storageClassName: fast-storage
When volume provisioning is invoked, the parameter “type: pd-ssd” is passed to the CSI plugin “com.example.team/csi-driver” via a “CreateVolume” call. In response, the external volume plugin provisions a new volume and then automatically create a PersistentVolume object to represent the new volume. Kubernetes then binds the new PersistentVolume object to the PersistentVolumeClaim, making it ready to use.
If the “fast-storage” StorageClass is marked default, there is no need to include the storageClassName in the PersistentVolumeClaim, it will be used by default.
Pre-Provisioned Volumes
You can always expose a pre-existing volume in Kubernetes by manually creating a PersistentVolume object to represent the existing volume. The following PersistentVolume, for example, exposes a volume with the name “existingVolumeName” belonging to a CSI storage plugin called “com.example.team/csi-driver”.
apiVersion: v1
kind: PersistentVolume
metadata:
name: my-manually-created-pv
spec:
capacity:
storage: 5Gi
accessModes:
- ReadWriteOnce
persistentVolumeReclaimPolicy: Retain
csi:
driver: com.example.team/csi-driver
volumeHandle: existingVolumeName
readOnly: false
Attaching and Mounting
You can reference a PersistentVolumeClaim that is bound to a CSI volume in any pod or pod template.
kind: Pod
apiVersion: v1
metadata:
name: my-pod
spec:
containers:
- name: my-frontend
image: dockerfile/nginx
volumeMounts:
- mountPath: "/var/www/html"
name: my-csi-volume
volumes:
- name: my-csi-volume
persistentVolumeClaim:
claimName: my-request-for-storage
When the pod referencing a CSI volume is scheduled, Kubernetes will trigger the appropriate operations against the external CSI plugin (ControllerPublishVolume, NodePublishVolume, etc.) to ensure the specified volume is attached, mounted, and ready to use by the containers in the pod.
For more details please see the CSI implementation design doc and documentation.
How do I create a CSI driver?
Kubernetes is as minimally prescriptive on the packaging and deployment of a CSI Volume Driver as possible. The minimum requirements for deploying a CSI Volume Driver on Kubernetes are documented here.
The minimum requirements document also contains a section outlining the suggested mechanism for deploying an arbitrary containerized CSI driver on Kubernetes. This mechanism can be used by a Storage Provider to simplify deployment of containerized CSI compatible volume drivers on Kubernetes.
As part of this recommended deployment process, the Kubernetes team provides the following sidecar (helper) containers:
-
- Sidecar container that watches Kubernetes VolumeAttachment objects and triggers ControllerPublish and ControllerUnpublish operations against a CSI endpoint.
-
- Sidecar container that watches Kubernetes PersistentVolumeClaim objects and triggers CreateVolume and DeleteVolume operations against a CSI endpoint.
-
- Sidecar container that registers the CSI driver with kubelet (in the future), and adds the drivers custom NodeId (retrieved via GetNodeID call against the CSI endpoint) to an annotation on the Kubernetes Node API Object
Storage vendors can build Kubernetes deployments for their plugins using these components, while leaving their CSI driver completely unaware of Kubernetes.
Where can I find CSI drivers?
CSI drivers are developed and maintained by third-parties. You can find example CSI drivers here, but these are provided purely for illustrative purposes, and are not intended to be used for production workloads.
What about Flex?
The Flex Volume plugin exists as an exec based mechanism to create “out-of-tree” volume plugins. Although it has some drawbacks (mentioned above), the Flex volume plugin coexists with the new CSI Volume plugin. SIG Storage will continue to maintain the Flex API so that existing third-party Flex drivers (already deployed in production clusters) continue to work. In the future, new volume features will only be added to CSI, not Flex.
What will happen to the in-tree volume plugins?
Once CSI reaches stability, we plan to migrate most of the in-tree volume plugins to CSI. Stay tuned for more details as the Kubernetes CSI implementation approaches stable.
What are the limitations of alpha?
The alpha implementation of CSI has the following limitations:
- The credential fields in CreateVolume, NodePublishVolume, and ControllerPublishVolume calls are not supported.
- Block volumes are not supported; only file.
- Specifying filesystems is not supported, and defaults to ext4.
- CSI drivers must be deployed with the provided “external-attacher,” even if they don’t implement “ControllerPublishVolume”.
- Kubernetes scheduler topology awareness is not supported for CSI volumes: in short, sharing information about where a volume is provisioned (zone, regions, etc.) to allow k8s scheduler to make smarter scheduling decisions.
What’s next?
Depending on feedback and adoption, the Kubernetes team plans to push the CSI implementation to beta in either 1.10 or 1.11.
How Do I Get Involved?
This project, like all of Kubernetes, is the result of hard work by many contributors from diverse backgrounds working together. A huge thank you to Vladimir Vivien (vladimirvivien), Jan Šafránek (jsafrane), Chakravarthy Nelluri (chakri-nelluri), Bradley Childs (childsb), Luis Pabón (lpabon), and Saad Ali (saad-ali) for their tireless efforts in bringing CSI to life in Kubernetes.
If you’re interested in getting involved with the design and development of CSI or any part of the Kubernetes Storage system, join the Kubernetes Storage Special-Interest-Group (SIG). We’re rapidly growing and always welcome new contributors.
- Introducing kustomize; Template-free Configuration Customization for Kubernetes May 29
- Getting to Know Kubevirt May 22
- Gardener - The Kubernetes Botanist May 17
- Docs are Migrating from Jekyll to Hugo May 5
- Announcing Kubeflow 0.1 May 4
- Current State of Policy in Kubernetes May 2
- Developing on Kubernetes May 1
- Zero-downtime Deployment in Kubernetes with Jenkins Apr 30
- Kubernetes Community - Top of the Open Source Charts in 2017 Apr 25
- Local Persistent Volumes for Kubernetes Goes Beta Apr 13
- Container Storage Interface (CSI) for Kubernetes Goes Beta Apr 10
- Fixing the Subpath Volume Vulnerability in Kubernetes Apr 4
- Principles of Container-based Application Design Mar 15
- Expanding User Support with Office Hours Mar 14
- How to Integrate RollingUpdate Strategy for TPR in Kubernetes Mar 13
- Apache Spark 2.3 with Native Kubernetes Support Mar 6
- Kubernetes: First Beta Version of Kubernetes 1.10 is Here Mar 2
- Reporting Errors from Control Plane to Applications Using Kubernetes Events Jan 25
- Core Workloads API GA Jan 15
- Introducing client-go version 6 Jan 12
- Extensible Admission is Beta Jan 11
- Introducing Container Storage Interface (CSI) Alpha for Kubernetes Jan 10
- Kubernetes v1.9 releases beta support for Windows Server Containers Jan 9
- Five Days of Kubernetes 1.9 Jan 8
- Introducing Kubeflow - A Composable, Portable, Scalable ML Stack Built for Kubernetes Dec 21
- Kubernetes 1.9: Apps Workloads GA and Expanded Ecosystem Dec 15
- Using eBPF in Kubernetes Dec 7
- PaddlePaddle Fluid: Elastic Deep Learning on Kubernetes Dec 6
- Autoscaling in Kubernetes Nov 17
- Certified Kubernetes Conformance Program: Launch Celebration Round Up Nov 16
- Kubernetes is Still Hard (for Developers) Nov 15
- Securing Software Supply Chain with Grafeas Nov 3
- Containerd Brings More Container Runtime Options for Kubernetes Nov 2
- Kubernetes the Easy Way Nov 1
- Enforcing Network Policies in Kubernetes Oct 30
- Using RBAC, Generally Available in Kubernetes v1.8 Oct 28
- It Takes a Village to Raise a Kubernetes Oct 26
- kubeadm v1.8 Released: Introducing Easy Upgrades for Kubernetes Clusters Oct 25
- Five Days of Kubernetes 1.8 Oct 24
- Introducing Software Certification for Kubernetes Oct 19
- Request Routing and Policy Management with the Istio Service Mesh Oct 10
- Kubernetes Community Steering Committee Election Results Oct 5
- Kubernetes 1.8: Security, Workloads and Feature Depth Sep 29
- Kubernetes StatefulSets & DaemonSets Updates Sep 27
- Introducing the Resource Management Working Group Sep 21
- Windows Networking at Parity with Linux for Kubernetes Sep 8
- Kubernetes Meets High-Performance Computing Aug 22
- High Performance Networking with EC2 Virtual Private Clouds Aug 11
- Kompose Helps Developers Move Docker Compose Files to Kubernetes Aug 10
- Happy Second Birthday: A Kubernetes Retrospective Jul 28
- How Watson Health Cloud Deploys Applications with Kubernetes Jul 14
- Kubernetes 1.7: Security Hardening, Stateful Application Updates and Extensibility Jun 30
- Draft: Kubernetes container development made easy May 31
- Managing microservices with the Istio service mesh May 31
- Kubespray Ansible Playbooks foster Collaborative Kubernetes Ops May 19
- Kubernetes: a monitoring guide May 19
- Dancing at the Lip of a Volcano: The Kubernetes Security Process - Explained May 18
- How Bitmovin is Doing Multi-Stage Canary Deployments with Kubernetes in the Cloud and On-Prem Apr 21
- RBAC Support in Kubernetes Apr 6
- Configuring Private DNS Zones and Upstream Nameservers in Kubernetes Apr 4
- Advanced Scheduling in Kubernetes Mar 31
- Scalability updates in Kubernetes 1.6: 5,000 node and 150,000 pod clusters Mar 30
- Five Days of Kubernetes 1.6 Mar 29
- Dynamic Provisioning and Storage Classes in Kubernetes Mar 29
- Kubernetes 1.6: Multi-user, Multi-workloads at Scale Mar 28
- The K8sPort: Engaging Kubernetes Community One Activity at a Time Mar 24
- Deploying PostgreSQL Clusters using StatefulSets Feb 24
- Containers as a Service, the foundation for next generation PaaS Feb 21
- Inside JD.com's Shift to Kubernetes from OpenStack Feb 10
- Run Deep Learning with PaddlePaddle on Kubernetes Feb 8
- Highly Available Kubernetes Clusters Feb 2
- Running MongoDB on Kubernetes with StatefulSets Jan 30
- Fission: Serverless Functions as a Service for Kubernetes Jan 30
- How we run Kubernetes in Kubernetes aka Kubeception Jan 20
- Scaling Kubernetes deployments with Policy-Based Networking Jan 19
- A Stronger Foundation for Creating and Managing Kubernetes Clusters Jan 12
- Kubernetes UX Survey Infographic Jan 9
- Kubernetes supports OpenAPI Dec 23
- Cluster Federation in Kubernetes 1.5 Dec 22
- Windows Server Support Comes to Kubernetes Dec 21
- StatefulSet: Run and Scale Stateful Applications Easily in Kubernetes Dec 20
- Introducing Container Runtime Interface (CRI) in Kubernetes Dec 19
- Five Days of Kubernetes 1.5 Dec 19
- Kubernetes 1.5: Supporting Production Workloads Dec 13
- From Network Policies to Security Policies Dec 8
- Kompose: a tool to go from Docker-compose to Kubernetes Nov 22
- Kubernetes Containers Logging and Monitoring with Sematext Nov 18
- Visualize Kubelet Performance with Node Dashboard Nov 17
- CNCF Partners With The Linux Foundation To Launch New Kubernetes Certification, Training and Managed Service Provider Program Nov 8
- Modernizing the Skytap Cloud Micro-Service Architecture with Kubernetes Nov 7
- Bringing Kubernetes Support to Azure Container Service Nov 7
- Tail Kubernetes with Stern Oct 31
- Introducing Kubernetes Service Partners program and a redesigned Partners page Oct 31
- How We Architected and Run Kubernetes on OpenStack at Scale at Yahoo! JAPAN Oct 24
- Building Globally Distributed Services using Kubernetes Cluster Federation Oct 14
- Helm Charts: making it simple to package and deploy common applications on Kubernetes Oct 10
- Dynamic Provisioning and Storage Classes in Kubernetes Oct 7
- How we improved Kubernetes Dashboard UI in 1.4 for your production needs Oct 3
- How we made Kubernetes insanely easy to install Sep 28
- How Qbox Saved 50% per Month on AWS Bills Using Kubernetes and Supergiant Sep 27
- Kubernetes 1.4: Making it easy to run on Kubernetes anywhere Sep 26
- High performance network policies in Kubernetes clusters Sep 21
- Creating a PostgreSQL Cluster using Helm Sep 9
- Deploying to Multiple Kubernetes Clusters with kit Sep 6
- Cloud Native Application Interfaces Sep 1
- Security Best Practices for Kubernetes Deployment Aug 31
- Scaling Stateful Applications using Kubernetes Pet Sets and FlexVolumes with Datera Elastic Data Fabric Aug 29
- SIG Apps: build apps for and operate them in Kubernetes Aug 16
- Kubernetes Namespaces: use cases and insights Aug 16
- Create a Couchbase cluster using Kubernetes Aug 15
- Challenges of a Remotely Managed, On-Premises, Bare-Metal Kubernetes Cluster Aug 2
- Why OpenStack's embrace of Kubernetes is great for both communities Jul 26
- The Bet on Kubernetes, a Red Hat Perspective Jul 21
- Happy Birthday Kubernetes. Oh, the places you’ll go! Jul 21
- A Very Happy Birthday Kubernetes Jul 21
- Bringing End-to-End Kubernetes Testing to Azure (Part 2) Jul 18
- Steering an Automation Platform at Wercker with Kubernetes Jul 15
- Dashboard - Full Featured Web Interface for Kubernetes Jul 15
- Cross Cluster Services - Achieving Higher Availability for your Kubernetes Applications Jul 14
- Citrix + Kubernetes = A Home Run Jul 14
- Thousand Instances of Cassandra using Kubernetes Pet Set Jul 13
- Stateful Applications in Containers!? Kubernetes 1.3 Says “Yes!” Jul 13
- Kubernetes in Rancher: the further evolution Jul 12
- Autoscaling in Kubernetes Jul 12
- rktnetes brings rkt container engine to Kubernetes Jul 11
- Minikube: easily run Kubernetes locally Jul 11
- Five Days of Kubernetes 1.3 Jul 11
- Updates to Performance and Scalability in Kubernetes 1.3 -- 2,000 node 60,000 pod clusters Jul 7
- Kubernetes 1.3: Bridging Cloud Native and Enterprise Workloads Jul 6
- Container Design Patterns Jun 21
- The Illustrated Children's Guide to Kubernetes Jun 9
- Bringing End-to-End Kubernetes Testing to Azure (Part 1) Jun 6
- Hypernetes: Bringing Security and Multi-tenancy to Kubernetes May 24
- CoreOS Fest 2016: CoreOS and Kubernetes Community meet in Berlin (& San Francisco) May 3
- Introducing the Kubernetes OpenStack Special Interest Group Apr 22
- SIG-UI: the place for building awesome user interfaces for Kubernetes Apr 20
- SIG-ClusterOps: Promote operability and interoperability of Kubernetes clusters Apr 19
- SIG-Networking: Kubernetes Network Policy APIs Coming in 1.3 Apr 18
- How to deploy secure, auditable, and reproducible Kubernetes clusters on AWS Apr 15
- Container survey results - March 2016 Apr 8
- Adding Support for Kubernetes in Rancher Apr 8
- Configuration management with Containers Apr 4
- Using Deployment objects with Kubernetes 1.2 Apr 1
- Kubernetes 1.2 and simplifying advanced networking with Ingress Mar 31
- Using Spark and Zeppelin to process big data on Kubernetes 1.2 Mar 30
- Building highly available applications using Kubernetes new multi-zone clusters (a.k.a. 'Ubernetes Lite') Mar 29
- AppFormix: Helping Enterprises Operationalize Kubernetes Mar 29
- How container metadata changes your point of view Mar 28
- Five Days of Kubernetes 1.2 Mar 28
- 1000 nodes and beyond: updates to Kubernetes performance and scalability in 1.2 Mar 28
- Scaling neural network image classification using Kubernetes with TensorFlow Serving Mar 23
- Kubernetes 1.2: Even more performance upgrades, plus easier application deployment and management Mar 17
- Kubernetes in the Enterprise with Fujitsu’s Cloud Load Control Mar 11
- ElasticBox introduces ElasticKube to help manage Kubernetes within the enterprise Mar 11
- State of the Container World, February 2016 Mar 1
- Kubernetes Community Meeting Notes - 20160225 Mar 1
- KubeCon EU 2016: Kubernetes Community in London Feb 24
- Kubernetes Community Meeting Notes - 20160218 Feb 23
- Kubernetes Community Meeting Notes - 20160211 Feb 16
- ShareThis: Kubernetes In Production Feb 11
- Kubernetes Community Meeting Notes - 20160204 Feb 9
- Kubernetes Community Meeting Notes - 20160128 Feb 2
- State of the Container World, January 2016 Feb 1
- Kubernetes Community Meeting Notes - 20160121 Jan 28
- Kubernetes Community Meeting Notes - 20160114 Jan 28
- Why Kubernetes doesn’t use libnetwork Jan 14
- Simple leader election with Kubernetes and Docker Jan 11
- Creating a Raspberry Pi cluster running Kubernetes, the installation (Part 2) Dec 22
- Managing Kubernetes Pods, Services and Replication Controllers with Puppet Dec 17
- How Weave built a multi-deployment solution for Scope using Kubernetes Dec 12
- Creating a Raspberry Pi cluster running Kubernetes, the shopping list (Part 1) Nov 25
- Monitoring Kubernetes with Sysdig Nov 19
- One million requests per second: Dependable and dynamic distributed systems at scale Nov 11
- Kubernetes 1.1 Performance upgrades, improved tooling and a growing community Nov 9
- Kubernetes as Foundation for Cloud Native PaaS Nov 3
- Some things you didn’t know about kubectl Oct 28
- Kubernetes Performance Measurements and Roadmap Sep 10
- Using Kubernetes Namespaces to Manage Environments Aug 28
- Weekly Kubernetes Community Hangout Notes - July 31 2015 Aug 4
- The Growing Kubernetes Ecosystem Jul 24
- Weekly Kubernetes Community Hangout Notes - July 17 2015 Jul 23
- Strong, Simple SSL for Kubernetes Services Jul 14
- Weekly Kubernetes Community Hangout Notes - July 10 2015 Jul 13
- Announcing the First Kubernetes Enterprise Training Course Jul 8
- Kubernetes 1.0 Launch Event at OSCON Jul 2
- How did the Quake demo from DockerCon Work? Jul 2
- The Distributed System ToolKit: Patterns for Composite Containers Jun 29
- Slides: Cluster Management with Kubernetes, talk given at the University of Edinburgh Jun 26
- Cluster Level Logging with Kubernetes Jun 11
- Weekly Kubernetes Community Hangout Notes - May 22 2015 Jun 2
- Kubernetes on OpenStack May 19
- Weekly Kubernetes Community Hangout Notes - May 15 2015 May 18
- Docker and Kubernetes and AppC May 18
- Kubernetes Release: 0.17.0 May 15
- Resource Usage Monitoring in Kubernetes May 12
- Weekly Kubernetes Community Hangout Notes - May 1 2015 May 11
- Kubernetes Release: 0.16.0 May 11
- AppC Support for Kubernetes through RKT May 4
- Weekly Kubernetes Community Hangout Notes - April 24 2015 Apr 30
- Borg: The Predecessor to Kubernetes Apr 23
- Kubernetes and the Mesosphere DCOS Apr 22
- Weekly Kubernetes Community Hangout Notes - April 17 2015 Apr 17
- Kubernetes Release: 0.15.0 Apr 16
- Introducing Kubernetes API Version v1beta3 Apr 16
- Weekly Kubernetes Community Hangout Notes - April 10 2015 Apr 11
- Faster than a speeding Latte Apr 6
- Weekly Kubernetes Community Hangout Notes - April 3 2015 Apr 4
- Paricipate in a Kubernetes User Experience Study Mar 31
- Weekly Kubernetes Community Hangout Notes - March 27 2015 Mar 28
- Kubernetes Gathering Videos Mar 23
- Welcome to the Kubernetes Blog! Mar 20