Everything You Need to Know About Azure Managed Disks

Everything You Need to Know About Azure Managed Disks

If you are looking for a reliable, scalable, and secure way to store your data in the cloud, you might want to consider Azure Managed Disks. In this article, I will introduce you to the concept of managed disks, how they differ from unmanaged disks, and what are the benefits and features of using them. I will also explain the different types of managed disks, how to backup and restore them, and how to leverage disk bursting and shared disks for optimal performance and availability.

What are managed disks and why use them?

Managed disks are Azure resources that provide you with durable and highly available block-level storage volumes for your virtual machines (VMs). Unlike unmanaged disks , where you have to create and manage your own storage accounts, managed disks are handled by Azure behind the scenes. This means that you don't have to worry about the complexity of storage account limits, access keys, or blob URIs. You just specify the size and type of disk you need, and Azure will create and attach it to your VM.

Some of the benefits of using managed disks are:

  • Simplified management: You only need to manage the disk resource, not the storage account. Azure handles the storage account creation, configuration, replication, encryption, and billing for you.
  • High availability: Managed disks are designed for 99.999% availability. Azure automatically replicates your data within the same region or across zones, depending on the type of disk you choose. You can also use availability sets or availability zones to ensure that your VMs and disks are distributed across fault domains and update domains.
  • Scalability: Managed disks support up to 30000 IOPS and 2000 MB/s per disk, depending on the disk size and type. You can also resize your disks or change their type without detaching them from your VMs. You can scale up to 1000 managed disks per subscription, per region.
  • Security: Managed disks are encrypted at rest by default, using Azure Storage Service Encryption (SSE) with Microsoft-managed keys or customer-managed keys . Azure also provides two additional encryption options: Azure Disk Encryption (ADE) and Encryption at Host. ADE encrypts your disks at the OS level, using BitLocker for Windows or DM-Crypt for Linux. On the other hand, Encryption at Host is applied at the host level, ensuring that all temp disks and disk caches are encrypted at rest and flow encrypted to the Storage clusters.
  • Integration: Managed disks are integrated with other Azure services, such as Azure Backup, Azure Site Recovery, Azure Monitor, Azure Security Center, and Azure Policy. You can use these services to backup, recover, monitor, secure, and audit your disks.

What are the types of managed disks?

Azure offers five types of managed disks: Standard HDD, Standard SSD, Premium SSD, Premium SSD v2, and Ultra Disk. Each type has different performance characteristics, availability options, and pricing models. Here is a brief overview of each type:

  1. Standard HDD: This is the most cost-effective type of disk for infrequently accessed data. It uses magnetic drives and offers up to 500 IOPS and 60 MB/s per disk. It supports zone-redundant storage (ZRS) replication for higher availability across zones.
  2. Standard SSD: This is a low-cost SSD option for web servers, lightly used enterprise applications, and dev/test environments. It offers better performance and reliability than HDDs, with up to 6000 IOPS and 750 MB/s per disk. It supports ZRS replication as well.
  3. Premium SSD: This is a high-performance SSD option for production workloads that require consistent low latency and high throughput. It offers up to 20000 IOPS and 900 MB/s per disk for P60 and larger disk sizes. It supports only locally redundant storage (LRS) replication within a single zone but offers single-instance SLA of 99.9% availability.
  4. Premium SSD v2: This is an enhanced version of Premium SSD that offers higher performance and larger disk sizes. It offers up to 30000 IOPS and 2000 MB/s per disk for P80 and larger disk sizes. It supports LRS replication as well but offers single-instance SLA of 99.95% availability.
  5. Ultra Disk: This is the fastest and most flexible type of disk for extremely demanding workloads that require sub-millisecond latency and massive throughput. It offers up to 160000 IOPS and 2000 MB/s per disk for Ultra Disk sizes above 4 GiB. It supports LRS replication as well but does not offer any SLA guarantees.

The following table summarizes the main differences between the types of managed disks:

Managed Disk Comparison


How to backup disks?

One of the most important aspects of managing your data is ensuring that you have a backup strategy in case of any disaster or accidental deletion. Azure provides several options to backup your managed disks, such as:

  • Azure Backup : This is a service that allows you to create scheduled or on-demand backups of your disks to a recovery services vault. You can restore your disks from any point in time within the retention period that you specify. Azure Backup supports all types of managed disks and offers incremental backups, which means that only the changes since the last backup are transferred, reducing the storage and network costs.
  • Azure Site Recovery : This is a service that allows you to replicate your disks to another region or zone for disaster recovery purposes. You can failover your VMs to the secondary location in case of an outage or planned maintenance. Azure Site Recovery supports all types of managed disks and offers near-synchronous replication, which means that the data lag between the primary and secondary location is minimal.
  • Snapshots : These are point-in-time copies of your disks that you can create manually or programmatically using Azure CLI, PowerShell, or SDKs. You can use snapshots to create new disks or restore existing disks. Snapshots are stored as standard page blobs in your storage account and are billed accordingly. Snapshots support all types of managed disks except Ultra Disk.

For Premium SSD disks, Azure also offers a new feature called incremental snapshots , which are similar to regular snapshots but with some advantages:

  • Incremental snapshots are stored as differential disks in a separate resource group called IncrementalSnapshotsRG, which is automatically created and managed by Azure. This means that you don't have to worry about the storage account limits or access keys.
  • Incremental snapshots are billed based on the actual used space, not the provisioned size of the disk. This means that you pay only for the changes since the previous snapshot, not the entire disk size.
  • Incremental snapshots are faster to create and restore than regular snapshots, as they only transfer the delta blocks, not the entire disk data.

To use incremental snapshots, you need to enable the feature on your subscription using Azure CLI, PowerShell, or SDKs. You also need to create a disk access resource, which is a logical representation of the access control for your disk. You can then create and restore incremental snapshots using the same tools as regular snapshots.

What is disk bursting?

Disk bursting is a feature that allows your disks to temporarily exceed their baseline performance limits and achieve higher IOPS and throughput for a short period of time. This can be useful for scenarios where you have intermittent spikes in your disk activity, such as booting up your VMs, running batch jobs, or performing backups.

There are two types of disk bursting: credit-based and on-demand.

  1. Credit-based disk bursting: This is available for Standard SSD and smaller Premium SSD disks (P30 and below). It works by accumulating burst credits when your disk is operating below its baseline performance, and consuming them when your disk is bursting above its baseline. The amount of credits you can accumulate and consume depends on the size and type of your disk. You can monitor your credit balance and burst performance using Azure Monitor metrics.
  2. On-demand disk bursting: This is available for larger Premium SSD disks (P40 and above) and Ultra Disk. It works by allowing your disk to burst up to the maximum performance limit of the disk size, regardless of the provisioned performance. You don't need to accumulate or consume any credits for this type of bursting. You only pay for the provisioned performance, not the burst performance.

What are shared disks and zone-redundant disks?

Shared disks and zone-redundant disks are two features that enhance the availability and scalability of your managed disks.

  • Shared disks: This feature allows you to attach a single Premium SSD or Ultra Disk to multiple VMs in the same region or zone. This enables you to run clustered or distributed applications that require concurrent access to the same disk, such as SQL Server Failover Cluster Instances (FCI), SAP ASCS/SCS, or Oracle RAC. You can enable shared disks on existing or new disks using Azure Portal, CLI, PowerShell, or SDKs. You can attach up to five VMs per disk, depending on the disk size and type.
  • Zone-redundant disks: This feature allows you to replicate your Standard HDD or Standard SSD disks across three availability zones in the same region. This increases the durability and availability of your disks in case of a zone failure or outage. You can enable zone-redundant disks on existing or new disks using Azure Portal, CLI, PowerShell, or SDKs. You can also combine zone-redundant disks with availability zones or sets to ensure that your VMs and disks are distributed across different fault domains and update domains.

Summary

In this article, I have explained what are managed disks, how they differ from unmanaged disks, and what are the benefits and features of using them. I have also covered the different types of managed disks, how to backup and restore them, and how to leverage disk bursting and shared disks for optimal performance and availability.

If you want to learn more about managed disks, you can refer to the following documentation:



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