Understanding Azure Storage: Managed Disks and Storage Accounts

Microsoft Azure cloud hero

Azure Storage is the foundation on which Azure provides scalable, durable, and highly-available storage for apps, data, and virtual machines (VMs) in the cloud. In this first part of Understanding Azure Storage, I’ll explain the difference between general purpose and blob storage accounts, and how Managed Disks can be used to deploy VMs and Virtual Machine Scale Sets (VMSS) faster.



If in the past, access to large-scale compute resources required a significant upfront investment in data center hardware, one of the key benefits of cloud computing, especially for smaller businesses, is that it gives everyone access to massively scalable computing power. Also, pooling resources in the cloud is more efficient because when not in use by one customer, rather than remaining idle, they can be assigned to another.

Azure Storage manages how disk size and I/O capacity are assigned to applications by load balancing data based on the traffic generated by an app, so as demand grows, Azure Storage adds disk capacity as required. While primarily intended for cloud apps, Azure Storage can also be used by apps running on local devices and on-premises servers. For high-performance workloads, the Premium Storage tier provides low-latency disk support for Azure-based VMs.

Managed Disks

If understanding Azure Storage and creating storage accounts seems like too much hard work, then Microsoft has made it easy to create VMs in Azure without needing to worry about configuring a storage account. Using Managed Disks, the process of creating a storage account and defining a URI for the disk can be skipped. Just specify the disk name, storage account type, and a few other parameters when deploying a VM, and that’s it.

Managed Disks also automate storage account scale management, allowing Virtual Machine Scale Sets (VMSS) to scale up to one thousand VMs in a single set, 10 times more than was possible with unmanaged disks.

For more information on using Managed Disks, see What are Azure Managed Disks? on the Petri IT Knowledgebase.

Azure Storage Accounts

There are two types of storage accounts: general purpose and blob. Blob storage accounts are for block and append blobs, and don’t support page blobs. They differ from general purpose accounts in that the Access Tier — not to be confused with performance tier — attribute allows you to choose between hot and cool storage. If data will be accessed infrequently, cool storage allows data to be stored at a lower cost. Hot storage is for frequently accessed data and can be stored at lower access cost. Only general purpose storage accounts have access to standard and premium performance tiers.

Storage account owners are the only users to have access by default. Azure manages access to storage using a shared key model, although blob storage can be configured to allow anonymous access. Each storage account is assigned two private access keys, allowing one key to be regenerated while the second is used to ensure access to the account isn’t lost as the other key is regenerated. Shared Access Signatures (SAS) can also be used to grant access to objects in storage without revealing a storage account key. For more information on SAS, see Understanding Shared Access Signatures (SAS) on Petri.

In this article, I explained how Managed Disks can be used to provision VMs and VMSS more easily, and the differences between general purpose and blob storage accounts. In part two of this series, I’ll go through the four storage types and different redundancy options.