Azure Managed Disks GA & Backup In Preview

Azure Managed Disks became GA a few weeks ago and offer much simpler disk management for Azure IaaS VMs by managing the storage accounts associated with the VM disks. You only have to specify the type (Premium or Standard) and the size of disk you need, and Azure creates and manages the disk for you.

As of today Microsoft have also announced preview support for Azure Backup with Azure Managed Disk VMs – so not quite there for those of us using Azure Backup with production VMs but certainly time to get playing (unless you don’t need to use Azure Backup – in which case get going into prod!).

It is also great to see that Microsoft haven’t left the “how do we migrate” conundrum as they often have done in the past. They are providing a wealth of documentation on how to convert disks from a number of scenarios even including an Azure Classic VM conversion into ARM with Managed Disks – https://docs.microsoft.com/en-us/azure/virtual-machines/virtual-machines-windows-migrate-to-managed-disks

Benefits

Simple and scalable VM deployment

Managed Disks handles storage for you behind the scenes. Previously, you had to create storage accounts to hold the disks (VHD files) for your Azure VMs. When scaling up, you had to make sure you created additional storage accounts so you didn’t exceed the IOPS limit for storage with any of your disks. With Managed Disks handling storage, you are no longer limited by the storage account limits (such as 20,000 IOPS / account). You also no longer have to copy your custom images (VHD files) to multiple storage accounts. You can manage them in a central location – one storage account per Azure region – and use them to create hundreds of VMs in a subscription.

Managed Disks will allow you to create up to 10,000 VM disks in a subscription, which will enable you to create thousands of VMs in a single subscription. This feature also further increases the scalability of Virtual Machine Scale Sets (VMSS) by allowing you to create up to a thousand VMs in a VMSS using a Marketplace image.

Better reliability for Availability Sets

Managed Disks provides better reliability for Availability Sets by ensuring that the disks of VMs in an Availability Set are sufficiently isolated from each other to avoid single points of failure. It does this by automatically placing the disks in different storage scale units (stamps). If a stamp fails due to hardware or software failure, only the VM instances with disks on those stamps fail. For example, let’s say you have an application running on five VMs, and the VMs are in an Availability Set. The disks for those VMs won’t all be stored in the same stamp, so if one stamp goes down, the other instances of the application continue to run.

Better security

You can use Azure Role-Based Access Control (RBAC) to assign specific permissions for a managed disk to one or more users. Managed Disks exposes a variety of operations, including read, write (create/update), delete, export, and retrieving a shared access signature (SAS) URI for the disk. You can grant access to only the operations a person needs to perform his job. For example, if you don’t want a person to copy a managed disk to a storage account, you can choose not to grant access to the export action for that managed disk. Similarly, if you don’t want a person to use an SAS URI to copy a managed disk, you can choose not to grant that permission to the managed disk.