Proposal: Data Disk restore from Image

docs/proposals/datadisk-snapshot-restore.md

@@ -0,0 +1,79 @@
+---
+title: Data Disk Restore From Snapshot
+creation-date: 2025-04-05
+status: implementable
+authors:
+- "@elankath"
+reviewers:
+- "@rishabh-11"
+- "@unmarshall"
+- "@kon-angelo "
+---
+
+# Data Disk Restore From Snapshot
+
+## 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 snapshots
+
+## Motivation
+The primary motivation is to support [Integration of vSMP MemeoryOne in Azure #](https://github.com/gardener/gardener-extension-provider-azure/issues/788). 
+Since we already implemented this for AWS via [Support for data volume snapshot ID ](https://github.com/gardener/gardener-extension-provider-aws/pull/112), we should introduce this enhancement
+in Azure as well.
+
+### 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 from a snapshot id.
+
+
+## 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
+    snapshotName: snap-1234
+  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 `snap-1234` represents the snapshot name created by an external process/tool.
+See [az-snapshot-create](https://learn.microsoft.com/en-us/cli/azure/snapshot?view=azure-cli-latest#az-snapshot-create).
+
+The Azure disk `snapshotName` is distinct from the azure `snapshotID`. The azure disk `snapshotID` is a full qualified hierarchical
+identifier that includes the `snapshotName`, Azure subscription ID and resource group name: 
+like `/subscriptions/<AzureSubscriptionID>/resourceGroups/<resourceGroupName>/providers/Microsoft.Compute/disks/<snapshotName>`
+
+It would be painful and errorprone to specify this in the shoot `WorkerConfig` section, so it is best that the MCM Azure provider take care
+of forming the fully qualified azure disk `snapshotID` and forming the `MachineClass` for azure which is then operated on by MCM Azure Provider.
+
+