Proposal: Data Disk restore from Image

docs/proposals/datadisk-image-restore.md

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+---
+title: Data Disk Restore From Image
+creation-date: 2025-04-05
+status: implementable
+authors:
+- "@elankath"
+reviewers:
+- "@rishabh-11"
+- "@unmarshall"
+- "@kon-angelo "
+---
+
+# Data Disk Restore From Image
+
+## Table of Contents
+
+- [Summary](#summary)
+- [Motivation](#motivation)
+    - [Goals](#goals)
+    - [Non-Goals](#non-goals)
+- [Proposal](#proposal)
+- [Alternatives](#alternatives)
+
+## Summary
+
+Currently, we have no support either in the shoot spec or in the [MCM Azure](https://github.com/gardener/machine-controller-manager-provider-azure) for restoring Azure Data Disks from a user created image.
+
+## Motivation
+The primary motivation is to support [Integration of vSMP MemeoryOne in Azure #](https://github.com/gardener/gardener-extension-provider-azure/issues/788). 
+We implemented support for this in AWS via [Support for data volume snapshot ID ](https://github.com/gardener/gardener-extension-provider-aws/pull/112).
+In Azure we have the option to restore data disk from a custom image which is more convenient and flexible. 
+
+### Goals
+
+1. Extend the provider specific [WorkerConfig](https://github.com/gardener/gardener-extension-provider-azure/blob/master/docs/usage/usage.md#workerconfig) section in the shoot YAML 
+ and support provider configuration for data-disks to support data-disk creation based on an existing image.
+
+
+## Proposal
+
+### Shoot Specification
+
+At this current time, there is no support for provider specific configuration of data disks in an azure shoot spec.
+The below shows an example configuration at the time of this proposal:
+```yaml
+providerConfig:
+  apiVersion: azure.provider.extensions.gardener.cloud/v1alpha1
+  kind: WorkerConfig
+  nodeTemplate: # (to be specified only if the node capacity would be different from cloudprofile info during runtime)
+    capacity:
+      cpu: 2
+      gpu: 1
+      memory: 50Gi
+```
+We propose that the worker config section be enahnced to support data disk configuration
+```yaml
+providerConfig:
+  apiVersion: azure.provider.extensions.gardener.cloud/v1alpha1
+  kind: WorkerConfig
+  dataVolumes: # <-- NEW SUB_SECTION
+  - name: vsmp1
+    imageReference: imgRef # ID or URN (publisher:offer:sku:version) of the image from which to create a disk
+    resourceGroup: # (optional) Name of resource group. Will take default if omitted
+  nodeTemplate: # (to be specified only if the node capacity would be different from cloudprofile info during runtime)
+   capacity:
+     cpu: 2
+     gpu: 1
+     memory: 50Gi
+```
+
+In the above `imgRef` specified via `providerConfig.dataVolumes.imageReference` represents the image ID or URN of the image from which to create a disk. This image should already exist.
+See [az image create](https://learn.microsoft.com/en-us/cli/azure/image?view=azure-cli-latest#az-image-create).
+An optional `resourceGroup` can be specified if the image is associated with a non-default Azure resource group.
+
+The [MCM Azure Provider](https://github.com/gardener/machine-controller-manager-provider-azure) will ensure that the data 
+disk is created with the _image reference_ set to the provided `imgRef`. See [az disk create](https://learn.microsoft.com/en-us/cli/azure/disk?view=azure-cli-latest#az-disk-create). 
+The mechanics of this is left to MCM Azure provider.
+
+