Earlier this year, Microsoft released Azure Managed Disks, a new feature that simplifies storage management for cloud admins -- and offers other benefits around availability, image capture and more.
The challenge with unmanaged disks is that they get complicated quickly. Each cloud storage account has limits in terms of overall capacity and how many IOPS are supported. This model means that admins likely need to create multiple storage accounts when they deploy multiple VMs. On top of that, administrators have to ensure that they don't exceed capacity limits and that each storage account can provide the IOPS required by all the disks within the account.
Azure Managed Disks simplify this process. They provide an abstraction layer that prevents the need for admins to create and manage storage accounts -- and their limits -- for virtual hard disks (VHD).
In addition to not having to worry about exceeding storage account limits, here are three more benefits of Azure Managed Disks:
To prevent single points of hardware failure, admins place VMs into availability sets. For example, they can put a load-balanced fleet of web servers into an availability set with multiple fault domains to ensure each VM runs on independent hardware. However, unmanaged disks don't provide that same guarantee. It's possible that all the disks for each VM in an availability set could end up in storage accounts placed on the same storage unit. Therefore, there's a potential single point of failure for storage when you use unmanaged disks, even when you place the VMs in an availability set.
Azure Managed Disks help eliminate that potential single point of failure for VM storage; they ensure that VMs in an availability set will use virtual disks placed on separate storage units.
Improved image capture process
VM images are great to speed up deployments. Once an image is built, admins can deploy servers repeatedly, using the same configuration and settings.
To capture unmanaged disk images, admins must use a command-line interface (CLI). With Azure Managed Disks, admins use a simple user interface in the Azure portal to capture an image. A managed image also includes managed data disks connected to a VM, so admins can capture both the managed OS disks and data disks as part of the process. Once admins capture a managed image, they can deploy new VMs based on that image without having to create new storage accounts or copy VHD files.
In addition to images, administrators can take independent snapshots of Azure Managed Disks. This allows them to make a point-in-time copy of an individual disk and to perform point-in-time recovery for data. With independent snapshots, admins can delete the parent disk, but the snapshot can persist for however long it's needed.
Admins can also use these snapshots to rebuild VMs from scratch. For example, if they require a point-in-time recovery for a VM, admins can create a new VM using the new managed disk based on a point-in-time snapshot. Admins can even place independent snapshots in a globally redundant storage account for disaster recovery.
Get started with Azure Managed Disks
Managed Disks offer performance tiers for Standard (hard disk drive) and Premium (solid-state drive) storage. To get started, select the Azure Managed Disks option when you create a VM in the portal, as shown in Figure 1.
In addition to provisioning VMs with Azure Managed Disks in the portal, admins can use PowerShell, the Azure CLI and Azure Resource Manager templates for automated deployments.
If you already use unmanaged disks and your VMs are in a region that supports Azure Managed Disks, you can migrate to the new feature. The process entails the use of a PowerShell command to perform the conversion after the VM is deallocated. Microsoft provides a collection of scripts on how to perform the migration. Keep in mind that the Azure Managed Disks feature is still new and is currently not available in the Azure Government regions.
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