Azure Managed Disks VS Unmanaged Disks/Storage Accounts

What is Azure managed disks?

Azure Managed Disks simplifies 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.

What is Azure Storage accounts or unmanaged disks?

Microsoft Azure unmanaged disk is a Microsoft-managed cloud service that provides storage that is highly available, secure, durable, scalable, and redundant. Microsoft takes care of maintenance and handles critical problems for you. Unmanaged disk consists of three data services: Blob storage, File storage, and Queue storage. In an unmanaged disk, you manage the storage accounts that you use to store the virtual hard disk (VHD) files that correspond to your VM disks. VHD files are stored as page blobs in Azure storage accounts.

Major difference between these

  1. Both have the choice to select from Premium or Standard options for the types of disks. Premium disks are SSD based and provide best IOPS one SSD itself can offer u tp 7500 IOPS where in standard option any disk size can only offer 500 IOPS.
  2. Unmanaged disks have various account limits interms of the TB (500 TB per storage account) per storage account, Ingress.egress storage. But managed disk does not have any limitations as such.
  3. The biggest advantage of managed disks are the enhanced availability features to separate the underlying storage units. In unmanaged the availability sets are managed under a single storage unit and it poses a risk for single point of failure.
  4. Next advantage of manage disk is the flexibility of storing and using the VM templates in a region. Unmanaged disk it increases the administration overhead when you have multiple storage accounts and you are using a golden OS image. This creates multiple copies of the same image across the storage accounts.
  5. Next advantage of Managed disk are when you need to upgrade your VM disks from standard to premium. Its very seamless in managed disks as you stop the VM and do the configurations to change the tier and then rebook the VM. It will take hardly 5 minutes where in unmanaged disks the process is tedious as there is no easy upgrade as managed types. You have to create a new premium storage account and copy the VHDs and create new VM on the premium account then copy any VM specific configurations across it going to time consuming and prone to human errors.
  6. Another advantage of managed disks are it supports downgrading from Premium to standard disk.

Here is how it looks the managed and unmanaged disk options for the VMs under Azure console. Head to head comparison for the standard disk in both Managed and Unmanaged options.

Managed Disk OS Disk options

Unmanaged Disk OS Disk options

Managed Disk Creating New Disk options

In Managed disk option the new disk source type can be used from an already taken snapshot and even a Storage blob also

Unmanaged Disk Creating New Disk options

Both the version support changing Host cache features.

The OS Disk has two ache options; which is Read/Write and Read only. By default, the host caching for OS Disk in Managed and Unmanaged disks type is Read&Write caching.

The Data Disk has three caching options which is Read/Write, Read Only and None. None is the default caching option for the data disks.

Managed – Advanced Disk options

If you look at the advanced options for the managed disk it provides an option for Creating Snapshots. Then an option to Export the disk as VHD and also I could see something more interesting options are coming soon such as Moving the disk to another subscription or another resource group.

Creating Snapshot option under the Managed Disk

 

Un managed – Advanced Disk options

Unmanaged disk does not give any features as Managed one.

So that’s the high level details for the Managed and Unmanaged disk options.

Courtesy Microsoft.com and Portal.Azure.com

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