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VM Disk Redundancy

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AZ-103 Exam Preparation: Microsoft Azure Administrator
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Developing, Implementing and Managing Azure Infrastructure
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3 Pillars of the Azure Cloud
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Overview of the course
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Duration2h 17m


Azure Resource Manager Virtual Machines

Virtual Machines are a very foundational and fundamental resource in Cloud Computing. Deploying virtual machines gives you more flexibility and control over your cloud infrastructure and services, however, it also means you have more responsibility to maintain and configure these resources. This course gives you an overview of why use virtual machines as well as how to create, configure, and monitor VMs in Azure Resource Manager.

Azure Resource Manager Virtual Machines: What You'll Learn

Lesson What you'll learn
Overview Overview of the course and the Learning Objectives
What is a Virtual Machine? Understand what are Azure Virtual Machines and what workloads are ideal for VMs
Creating and Connecting to Azure VMs Learn to deploy Windows and Linux VMs as well as how to connect to these VMs
Scaling Azure Virtual Machines Understand VM scaling, load-balancing, and Availability Sets in Azure Resource Manager
Configuration Management Understand the basic concepts of Desired State Configuration and the options available to Azure VMs
Design and Implement VM Storage Gain an understanding of the underlying Storage options available to VMs as well as Encryption
Configure Monitoring & Alerts for Azure VMs Learn to monitor VMs in Azure Resource Manager as well as configure alerts.
Summary Course summary and conclusion



We’ve already created several virtual machines up until this point, but we want to take a closer look at the storage options we have when building our VMs. These include Standard vs Premium storage and Managed vs Unmanaged disks.

We’ve referred to Standard and Premium storage options all throughout this lesson thus far, but we haven’t defined what they actually look like. Standard storage is made up of your typical magnetic drives referred to as HDD drives and is the cheapest option available. This type of storage is best suited for storing large amounts of data where data is accessed infrequently. But also I’ve found this works out just fine for demo purposes or to quickly setup a Dev box. Premium storage like the name says is a higher-tier and more costly option that is made up of SSDs, or Solid-State Disks providing low-latency and faster I/O performance. Premium storage is best suited for heavy I/O applications like SQL Server databases. Once you setup your VM disk as Standard or Premium you may not change or convert this option later

I’ve mentioned managed disks before in this course, but to recap, a Managed Disk is really a service that Azure provides which alleviates the work of you having to managed storage accounts. Azure will manage your disks and provide all the redundancy and replication options for you in the background. You can think of it as a single storage account. You just choose the your Storage type, Standard or Premium, and choose any option from these two tiers. It’s a more costly option than Unmanaged disks, however much of the overhead is taken away such as having to micro-manage your fault and update domains when doing virtual machine scale sets and availability sets as we’ve learned previously. Also you no longer have to worry about storage account Input/Output operation limits on your storage accounts. Managed disks integrate very well with other Azure services as well such as the Azure Backup service. This is important since managed disks can only be use with the LRS storage option and so for disaster recovery you want to use managed disks with the Azure Backup service. One last important detail: VMs with Managed Disks require outbound traffic on port 8443 to report the status of the installed VM extensions to the Azure platform, so be sure to unblock this port if using Managed Disks.

Unmanaged disks are your typical option where you choose to manage your own storage account as well as the VHD disks in those storage accounts. This is a cheaper option but you have to be careful with storage account limits including the maximum number of disks per storage account.

Let’s look back at the “Azure subscription and service limits, quotas, and constraints” documentation to view some of the limits of these virtual machine disk options.

Looking first at the Managed disks we can see the different Standard Disk type options to choose from based on the Disk Size, IOPS per disk, and Throughput per disk. We can see the same for the Premium storage option as well. Looking further down we can see the Unmanaged disks options. You’ll note that all unmanaged disks have a maximum disk size of 1 TB including the OS disk which is much greater than the 127GB maximum OS disk size we used to have in the past. Again, remember that even if you have a 1TB drive, you’re only charged for the amount of disk space you actually use and not for the capacity. One thing to callout here is the maximum number of unmanaged disks per storage account. We can see that Unmanaged Standard disks have a maximum disk count of 66 and 40 disks per storage account for the Basic and Standard tier respectively while Premium unmanaged disks have a maximum number of disk per storage account anywhere from 35 to 280 depending on the disk type.

One bonus tip before wrapping up this discussion is that if you create and upload your own custom VHD image to your unmanaged storage account then you can only build VMs that reside in the same storage account as your custom image storage account. To reuse the same VHD image to build a VM in a different storage account you will need to use a tool like AzCopy, PowerShell, Azure Storage Explorer, etc, to copy the image over to that storage account you wish to build your VM based on this custom image. With Managed disks, you upload it once and you can create hundreds of VMs based off this image without having to worry about storage account overhead.


About the Author

Learning paths1

Chris has over 15 years of experience working with top IT Enterprise businesses.  Having worked at Google helping to launch Gmail, YouTube, Maps and more and most recently at Microsoft working directly with Microsoft Azure for both Commercial and Public Sectors, Chris brings a wealth of knowledge and experience to the team in architecting complex solutions and advanced troubleshooting techniques.  He holds several Microsoft Certifications including Azure Certifications.

In his spare time, Chris enjoys movies, gaming, outdoor activities, and Brazilian Jiu-Jitsu.