KEP-3751: Kubernetes VolumeAttributesClass ModifyVolume

[sunnylovestiramisu]

• One-line PR description: Add capabilities to the Kubernetes Persistent Volume API to allow users dynamically control volume options

• Issue link: Kubernetes VolumeAttributesClass ModifyVolume #3751

/sig storage

[sunnylovestiramisu]

cc @gnufied @jingxu97

[jsafrane]

There should be some description about how current QoS setting in StorageClass parameters will affect namespace quota. Will it get copied (how?) from SCs to PVCs? Will this KEP disallow mixing QoS in StorageClass and in PVCs?

[sunnylovestiramisu]

Reading the release note - admission_control_resource_quota.md, it is not so clear to me what is the existing behavior. But I think for the QoS feature, it is risky to trigger an update to force the params within the ResourceQuota etc. Maybe we should design it in a way that does not reduce and only increase Iops/throughput in this situation.

[gnufied]

cc @derekwaynecarr

[xing-yang]

Please add a file with PRR approver like this: https://github.com/kubernetes/enhancements/blob/master/keps/prod-readiness/sig-storage/3107.yaml

[msau42]

Will let @xing-yang give final lgtm

[xing-yang]

/lgtm

[xing-yang]

/hold cancel

[johnbelamaric]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: johnbelamaric, msau42, sunnylovestiramisu

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[doubletao318]

@sunnylovestiramisu What is the difference of VolumeAttributesClass and StorageClass?

[carlory]

1. A StorageClass provides a way for administrators to describe the "classes" of storage they offer. Different classes might represent different or same storage vendors. And the StorageClassName field in pvc and pv is immutable after creation once it is set.

2. A VolumeAttributesClass is a way for administrators to describe the attributes class of volumes they offer. It's independent of storage vendors. Because the VolumeAttributesClass uses the opaque field to store the attributes, so in design, its cannot make sure that all the storage vendors can recognize and support the settings of volumes' attributes. There is no common standard for the attributes of volumes. It is up to the storage vendors to decide what attributes they support. And the VolumeAttributesClass field in pvc is mutable after creation.

3. The main difference between them is that they are used for different purposes. The StorageClass is used to provision the persistent volumes, and the VolumeAttributesClass is used to set the mutable attributes of volumes. i.e. IOPS and Throughput of volumes.

4. It's difficult to make the parameters field of the StorageClass mutable. And it's impossible to make the storageClassName field of the PersistentVolumeClaim mutable. So we need a new object to set the mutable attributes of volumes. And the VolumeAttributesClass is the best choice.

[carlory]

If I misunderstood your question and the KEP, please correct me. Thanks!

cc @doubletao318 @sunnylovestiramisu

[doubletao318]

@carlory
Thanks for your answer.

1. Now, most storage vendor provider the volume attributes in StorageClass, such as qos. Now we support VolumeAttributesClass, I think it is a challange for them.
2. For qos self, I also think there should one CR like StorageQoS, so the user can change QoS in PV level or in all PV level.

[carlory]

If you're interested in the implementation of the feature, you can find it in the github project. And we encourage some people to join us to implement the feature.

[PrasanaaV]

Hello, when I click on the link, I have a 404 error page. Sorry I am quite new to Kubernetes and opensource project.

[sunnylovestiramisu]

@PrasanaaV Since you are not a member of kubernetes-csi, you cannot see the board, if you want to apply for membership you can go through the application process.

However you can still see the open issues in k/k issues page related to this kep by searching "KEP-3751". You should be able to see those unassigned tasks.