What is NOT possible with Azure Backup

Before you prepare your environment for Azure Backup, be sure to understand these limitations:

* Backing up virtual machines with more than 16 data disks is not supported.

* Backing up virtual machines with a reserved IP address and no defined endpoint is not supported.

* Backing up Linux VMs encrypted through Linux Unified Key Setup (LUKS) encryption is not supported.

* Microsoft doesn't recommend backing up VMs that contain Cluster Shared Volumes (CSV) or Scale-Out File Server configuration. They require involving all VMs included in the cluster configuration during a snapshot task. Azure Backup doesn't support multi-VM consistency.

* Backup data doesn't include network mounted drives attached to a VM.

* Replacing an existing virtual machine during restore is not supported. If you attempt to restore the VM when the VM exists, the restore operation fails.

* Cross-region back up and restore are not supported.

* Backing up and restoring virtual machines using unmanaged disks in storage accounts with network rules applied, is not supported.

* While configuring back up, make sure the Firewalls and virtual networks storage account settings allow access from All networks.

* Restoring a domain controller (DC) VM that is part of a multi-DC configuration is supported only through PowerShell. To learn more, see Restoring a multi-DC domain controller.

* Restoring virtual machines that have the following special network configurations is supported only through PowerShell. VMs created through the restore workflow in the UI will not have these network configurations after the restore operation is complete:
- Virtual machines under load balancer configuration (internal and external)
- Virtual machines with multiple reserved IP addresses
- Virtual machines with multiple network adapters

* As of January 2018, you can create up to 25 Recovery Services vaults, per supported region of Azure Backup, per subscription. If you need additional vaults, create an additional subscription. You can register upto 200 Azure Virtual machines per vault.  As of April 2018, users can now create as many as 500 recovery services vaults in each subscription per region as compared to the earlier limit of 25 vaults per region per subscription.

You cannot “migrate” your backup data or vault between subscriptions

* Azure Backup supports a specified list of operating systems & their corresponding versions. Core OS Linux & versions older than Windows Server 2008 R2 are some that are not supported

* The backup process tries to complete a backup job as quickly as possible. In doing so, it consumes as many resources as it can. However, all I/O operations are limited by the Target Throughput for Single Blob, which has a limit of 60 MB per second.

* Since the Backup service is processing backups from multiple customers, copying backup data from snapshot to the backup or Recovery Services vault might not start immediately. In times of peak load, the wait can stretch up to eight hours due to the number of backups being processed. However, the total VM backup time is less than 24 hours for daily backup policies.

* Microsoft commits to at least 99.9% availability of the backup and restore functionality of the Azure Backup service. Availability is calculated over a monthly billing cycle.

* There are limits on when or how many times a backup job can be scheduled

* System Center DPM & Azure Backup Server cannot back up Oracle workloads

* Deduplication is not available in Azure for any Backup component. When System Center DPM and Backup Server are deployed in Azure, the storage disks attached to the VM cannot be deduplicated.

* Backup data stored in a vault can't be moved to a different vault.

* A Recovery Services vault can only change storage options before any backups have been stored. It is not possible to change from GRS to LRS after a backup

* Item Level Restore (ILR) for VMs backed up to a Recovery Services vault isn't supported

* A DPM or Azure Backup server can be registered to only one vault. The server cannot be registered to multiple vaults

* Size limits for data backup of Azure VM - 16 data disks, Data disk up to 4095 GB

* Azure Backup doesn't support deleting or purging individual items from stored backups.

* Backup policy does not consider Daylight Saving Time (DST)

Also see:
What is NOT supported on Azure Virtual Machines
What is NOT possible with Azure Managed Disks
What is NOT supported with Azure Site Recovery
Notes from Azure Backup Deep Dive Whitepaper

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