This question always pursues me, so I want to drop these lines in order to make it clear in my mind and for my customers:
With unmanaged disks, you are responsible for the storage accounts that are used to hold the VHDs that correspond to your VM disks. You pay the storage account rates for the amount of space you use, which is great, you pay for what you use.
A single storage account is capable of supporting 40 standard virtual hard disks at full throttle (20.000 IOPS). In case that you you need to scale out, you will need more than one storage account, which can get complicated.
Managed disks are the newer and recommended disk storage model. You only have to specify the disk type (Premium or Standard) and the size of the disk and automatically, Azure creates and manages both the disk and the storage it uses. You don’t have to worry about storage account limits, which makes them easier to scale out. They also offer several other benefits:
- Increased reliability: Azure ensures that VHDs associated with high-reliability VMs will be placed in different parts of Azure storage to provide similar levels of resilience.
- Better security: Managed disks are truly managed resources in the resource group. This means they can use role-based access control to restrict who can work with the VHD data.
- Snapshot support: Snapshots can be used to create a read-only copy of a VHD. You have to shut down the owning VM but creating the snapshot only takes a few seconds. Once it’s done, you can power on the VM and use the snapshot to create a duplicate VM to troubleshoot a production issue or rollback the VM to the point in time that the snapshot was taken.
- Backup support: Managed disks can be automatically backed up to different regions for disaster recovery with Azure Backup all without affecting the service of the VM.