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In our previous article we have discussed on, how to work with Azure Table Storage using C# . Today in this article we will discuss about the Overview Of Azure Disk Storage service.

Tool Installation Articles :

1. Configure Azure Command Line Interface ( Azure CLI) On Windows
2. Configure PowerShell For Microsoft Azure Az Module On Windows

Previous Azure Series :

1. Learn Basics Of Azure Networking In 60 Hours
2. Learn Basic Of Azure Active Directory And Azure Identity And Access Management
3. Azure DevOps – Learn at one place

If you have missed our previous articles on Azure Storage and Database Series, please check it in following links.

Part 1 – Overview Of Azure Storage and Database

Part 2 – Azure Storage Account

Part 3 – Azure Blob Storage

Part 4 – Work With Azure Blob Storage

Part 5 – Storage Explorer For Azure Storage

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Part 27 – Difference Between Azure Blog Storage And Azure File Storage

Part 28 – Azure Queue Storage – Overview

Part 29 – Azure Queue Storage – Store And Process Messages In Azure Queue

Part 30 – Azure Table Storage – Overview

Part 31 – Azure Table Storage – Work with Azure Table Storage

Next Article : Part 33 – Azure Disk Storage – Create And Attach Azure Data Disk To Azure VM

Azure Disk Storage

As we know it is designed to be used with Azure Virtual Machines and Azure VMware Solution (in preview). Azure Disk Storage offers high-performance, durable block storage for our business-critical applications and also provides robust support, when migrating our data center from on-premises to the cloud. Get high performance with sub-millisecond latency for throughput and transaction-intensive workloads such as SAP HANA, SQL Server and Oracle.

In case of Disk storage, Microsoft Azure providing following two options.

• Unmanaged Disk : Microsoft Azure unmanaged disk is a Microsoft-managed cloud service that provides storage that is highly available, secure, durable, scalable, and redundant. In an unmanaged disk, we must create and manage the storage accounts that we use to store the virtual hard disk (VHD) files that correspond to our VM disks. The price details can be found in this link.

• Managed Disk :  In Managed Disk Storage, we are no longer controlled by the storage account limits. We can have one storage account per region. The managed disk provides less access time, enhanced manageability and high availability which provides the following features. The price details can be found in this link.

In this article, we will discuss more on Managed disk, because of its popularity.

Benefits of Managed Disk

The Azure managed disk is a popular service provided by Microsoft Azure. It provides following benefits.

• Simple – Abstracts underlying storage account/blob associated with the Virtual Machine disks from customers. Eliminates the need to manage storage account for IaaS Virtual Machines (VMs)

• Azure Backup support – To protect against regional disasters, Azure Backup can be used to create a backup job with time-based backups and backup retention policies. Azure Backup offers Azure Disk Backup (preview) as a native, cloud-based backup solution that protects your data in managed disks. 

• Secure by default – Role based access control, storage encryption by default and encryption using own keys

• Storage account limits do not apply – No throttling due to storage account IOPS limits

• Integration with availability sets – Managed disks support Availability Sets to ensure that the disks of VMs in an availability set are sufficiently isolated from each other to avoid a single point of failure.

• Integration with Availability Zones – Managed disks support Availability Zones, to ensure a high-availability offering that protects our applications from datacenter failures. 

• Big scale – 50,000 VM disks of a type in a subscription per region

• Better Storage Resiliency – Prevents single points of failure due to storage Supports both Standard and Premium Storage disks.

Azure Disk Types

Azure provides different types of storage disk’s. Let’s go through the following dish types.

• Azure Standard HDD – Standard HDD is based on magnetic drives and designed for low priority workloads. Standard HDD is the cheapest solution among all other Azure disk type.

• Azure Standard SSD – Standard SSD is designed for light to moderate use. Microsoft provide 99% capacity and performance thresholds but not guaranteed.

• Azure Premium SSD – Premium SSD’s is designed for performance sensitive and for production environment. Only used with compatible VMs. Unlike standard SSD we will get reserved performance and capacity.

• Azure Ultra-Disk – Ultra-Disk provide high throughput, high IOPs and low latency. Ultra-disk provides configurable capacity and performance features.

As per Microsoft document, following table provides a comparison of ultra disks, premium solid-state drives (SSD), standard SSD, and standard hard disk drives (HDD) for managed disks to help you decide what to use.

Detail	Ultra disk	Premium SSD	Standard SSD	Standard HDD
Disk type	SSD	SSD	SSD	HDD
Scenario	IO-intensive workloads such as SAP HANA, top tier databases (for example, SQL, Oracle), and other transaction-heavy workloads.	Production and performance sensitive workloads	Web servers, lightly used enterprise applications and dev/test	Backup, non-critical, infrequent access
Max disk size	65,536 gibibyte (GiB)	32,767 GiB	32,767 GiB	32,767 GiB
Max throughput	2,000 MB/s	900 MB/s	750 MB/s	500 MB/s
Max IOPS	160,000	20,000	6,000	2,000

Storage Tiers in Azure

There are three types of storage tiers, so that you can store your data in most cost-effective manner and depending on how you use it.

• Hot Access Tier – Hot Access Tier is the one where the frequently used data resides. It has high storage costs and low access costs. For critical frequently used applications like SQL, Microsoft always recommends using Standard/Premium SSD as SSD already has Caching in it.

• Cool Access Tier – Cool Access Tier is the one where infrequently accessed data resides and stored for at least 30 day. It has lower storage costs and higher access costs compared to hot storage.

• Archive Access Tier – Archive Access Tier is used for storing data that is rarely accessed and stored for at least 180 days with flexible latency requirements. The archive backup storage tier is only available at the blob level and not at the storage account level.

Data Security

Following are several types of encryption available for our managed disks, to secure and protect our data from unauthenticated guest.

• Azure Disk Encryption (ADE) – It helps protect and safeguard our data to meet our organizational security and compliance commitments. ADE is integrated with Azure Key Vault to help us control and manage the disk encryption keys and secrets.

• Server-Side Encryption (SSE) (also known as Encryption-At-Rest) – It automatically encrypts data stored on Azure managed disks (OS and data disks) when persisting it to the cloud. 

• Encryption At Host – It ensures that data stored on the VM host is encrypted at rest and flows encrypted to the Storage service. Disks with encryption at host enabled are not encrypted with SSE; instead, the server hosting our VM provides the encryption for our data, and that encrypted data flows into Azure Storage.

Disk Roles

There are following three main disk roles in Azure. These roles map to disks of our virtual machine when it deployed.

• Data disk – A data disk is a managed disk that’s attached to a virtual machine to store application data, or other data we need to keep. Each data disk has a maximum capacity of 32,767 gibibytes (GiB)

• OS disk – Every virtual machine has one attached operating system disk. That OS disk has a pre-installed OS, which was selected when the VM was created. This disk contains the boot volume. This disk has a maximum capacity of 4,095 GiB.

• Temporary disk – Most VMs contain a temporary disk. The temporary disk provides short-term storage for applications and processes. Data on the temporary disk may be lost during a maintenance event or when you redeploy a VM but persist with a successful standard reboot of VM.

Redundancy Of Disks

Azure managed disks offer following two storage redundancy options,

• Locally-Redundant Storage (LRS) – It replicates our data three times within a single data center in the selected region. LRS protects our data against server rack and drive failures.

• Zone-Redundant Storage (ZRS) – It synchronously replicates our Azure managed disk across three Azure availability zones in the region we select. Each availability zone is a separate physical location with independent power, cooling, and networking. But there are following limitation in ZRS.
  • Only supported with premium solid-state drives (SSD) and standard SSDs
  • Currently available only in the West US 2, West Europe, North Europe, and France Central regions
  • Can’t currently be used with Azure Backup or Azure Site Recovery.

Disk Performance Metrics

Azure offers metrics in the Azure portal that provide insight on how our virtual machines (VM) and disks perform. The metrics can also be retrieved through an API call. This section divided into following three subsections,

• Disk IO, Throughput And Queue Depth Metrics – These metrics allow you to see the storage performance from the perspective of a disk and a virtual machine.
• Disk Bursting Metrics – These are the metrics provide observability into our bursting feature on our premium disks.
• Storage IO Utilization Metrics – These metrics help diagnose bottlenecks in our storage performance with disks.

Managed Disk Bursting

Azure offers the ability to boost disk storage IOPS and MB/s performance, this is referred to as bursting for both virtual machines (VM) and disks. Currently, following are two managed disk types that can burst,

• Premium SSDs
• Standard SSDs.

The following scenarios can benefit greatly from bursting.

• Improve startup times
• Handle batch jobs
• Traffic spikes

There are following two models of bursting for disks,

• An On-Demand Bursting Model (preview)
• A Credit-Based Model

Note : VM-level bursting only uses the credit-based model for bursting, it is enabled by default for all VMs that support it

With the above information, I am concluding this article. I hope this is informative to you. Please let me know if I missed anything important or if my understanding is not up to the mark. Keep reading, share your thoughts, experiences. Feel free to contact us to discuss more.

Next Article : Part 33 – Azure Disk Storage – Create And Attach Azure Data Disk To Azure VM

If you have any suggestion / feedback / doubt, you are most welcome. Stay tuned on Knowledge-Junction, will come up with more such articles.

Thanks for reading 🙂 .