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-# Azure RM Backup Vault Module
+# Azure Data Protection Backup Vault Module
 
-This module creates an Azure Recovery Services Backup Vault with the specified name, resource group, and location. 
+This module creates an Azure Data Protection Backup Vault with the specified name, resource group, and location.
+
+## Variables
+
+- `rg_name`: The name of the resource group where the backup vault will be created.
+- `location`: The Azure region where the backup vault will be created.
+- `base_name`: Optional base name used to generate a unique backup vault name when `name` is not set.
+- `name`: Optional explicit backup vault name. If omitted, the module generates a deterministic name from `base_name`.
+- `datastore_type`: Type of datastore for the backup vault. Allowed values: `ArchiveStore`, `OperationalStore`, `SnapshotStore`, `VaultStore`.
+- `redundancy`: Backup storage redundancy type. Allowed values: `GeoRedundant`, `LocallyRedundant`, `ZoneRedundant`.
+- `cross_region_restore_enabled`: Enables cross-region restore. Can only be set to `true` when `redundancy = "GeoRedundant"`.
+- `retention_duration_in_days`: Soft delete retention duration in days (`14` to `180`).
+- `immutability`: Immutability state. Allowed values: `Disabled`, `Locked`, `Unlocked`.
+- `soft_delete`: Soft delete state. Allowed values: `AlwaysOn`, `Off`, `On`.
+- `identity`: Optional managed identity configuration object:
+	- `type`: Identity type. Allowed values: `SystemAssigned`, `UserAssigned`, `SystemAssigned, UserAssigned`.
+	- `identity_ids`: Optional list of user-assigned identity IDs (required when `type = "UserAssigned"`).
+- `tags`: A map of tags to apply to the backup vault.
+
+## Usage scenarios
+
+- **Operational recovery**: Use Backup Vault to manage operational recovery workflows; exact datastore behavior is workload-specific. Example services/use cases: **AKS** (cluster state + PV snapshots), **Azure Blobs** (operational protection where data stays in the source account and backup policy also governs vaulted retention), and **Azure Files** (snapshot-based fast restore patterns).
+- **Long-term retention**: Use `VaultStore` for policy-based offsite retention and stronger isolation from production data. Example services/use cases: **Azure Blobs**, **Azure Files (vaulted backup)**, **Azure Database for PostgreSQL**, and **AKS** (vault-tier retention rules).
+- **Regional resiliency**: Use `VaultStore` with `redundancy = "GeoRedundant"` and `cross_region_restore_enabled = true` for paired-region restore scenarios. Example services/use cases: **AKS** and other vault-tier backup configurations where cross-region restore is supported.
+- **Compliance and low-cost cold retention**: Use `ArchiveStore` where supported for long-term retention with lower storage cost and slower retrieval. Example services/use cases: **Azure VMs**, **SQL Server in Azure VMs**, and **SAP HANA in Azure VMs** (subject to archive eligibility rules).
+
+> Compatibility differs by workload, region, and policy settings. Always confirm current support in the relevant Azure Backup support matrix before rollout.
+
+## Datastore types (concise)
+
+**OperationalStore** is the operational tier designed for faster recovery and short-to-medium retention windows. In Microsoft Learn examples (for example AKS), this tier keeps backup data within your tenant and is typically used for frequent restore points and day-to-day recovery operations.
+
+**VaultStore** is the vault-standard tier for offsite, policy-driven retention in Backup vault storage. It is commonly used when you want stronger isolation from production resources, longer retention than operational snapshots, and optional cross-region restore when combined with geo-redundant vault settings.
+
+**ArchiveStore** represents archive-style retention for infrequently accessed backup data and cost-optimized long-term preservation. Microsoft Learn notes that archive usage is workload-dependent and comes with constraints (such as eligibility and rehydration/restore behavior), so it is best suited for compliance-heavy scenarios rather than frequent restores.
+
+**SnapshotStore** is a legacy/compatibility datastore value that appears in provider schemas and older patterns. For newer Azure Backup workflows, Microsoft guidance and examples more often emphasize `OperationalStore` and `VaultStore`, with `OperationalStore` generally preferred over snapshot-style behavior for active operational protection.
+
+## References (Microsoft Learn)
+
+- [Overview of Azure Blob backup](https://learn.microsoft.com/azure/backup/blob-backup-overview)
+- [What is Azure Kubernetes Service backup?](https://learn.microsoft.com/azure/backup/azure-kubernetes-service-backup-overview#which-backup-storage-tier-does-aks-backup-support)
+- [Overview of Archive tier in Azure Backup](https://learn.microsoft.com/azure/backup/archive-tier-support)
+- [About Azure Files backup](https://learn.microsoft.com/azure/backup/azure-file-share-backup-overview)
+
+## Outputs
+
+- `backup_vault_id`: The ID of the created backup vault.
+- `backup_vault_name`: The name of the created backup vault.
+- `backup_vault_identity_principal_id`: Principal ID of the assigned managed identity, if configured.
+- `backup_vault_identity_tenant_id`: Tenant ID of the assigned managed identity, if configured.
+
+## Example Usage
+
+```hcl
+module "backup_vault" {
+	source = "./modules/backup-vault"
+
+	rg_name  = azurerm_resource_group.rg.name
+	location = azurerm_resource_group.rg.location
+
+	base_name = "bv"
+
+	datastore_type    = "VaultStore"
+	redundancy        = "LocallyRedundant"
+	soft_delete       = "On"
+	immutability      = "Disabled"
+	retention_duration_in_days = 14
+
+	tags = {
+		environment = "dev"
+	}
+}
+```