Azure Disk Storage Options Explained
When migrating your data center from on premises to Azure, you have a lot of disk storage options available. It is very common to get confused in a lot of options. In this article we’ll be covering most of the common storage options available in Azure.
Difference Between Managed Disks and Unmanaged Disks
Microsoft has launched a new type of Disk i.e. Managed Disk. This article discusses the differences between Azure Managed and Unmanaged disks
In unmanaged disks, you have to create storage accounts to hold the disks (VHD files) for your Azure VMs.
With Managed Disks, you are no longer limited by the storage account limits. You can have one storage account per Azure region.
Benefits of Using Managed Azure Disk Storage:
- Managed Disks provides better reliability for Availability Sets by ensuring that the disks of VMs in an Availability Set are sufficiently isolated from each other to avoid single points of failure
- Azure Disks are designed for 99.999% availability.
- Granular access control: You can grant access to only the operations a person needs to perform their job. For example, if you don’t want a person to copy a managed disk to a storage account, you can choose not to grant access to the export action for that managed disk.
|Is an ARM (Azure Resource Manager) object (resource)||Is not an ARM resource, but a file (.vhd) residing on an Azure Storage Account. The latter is an ARM object|
|The managed disks sizes are fixed (and can be resized). Which means that you cannot choose a custom size. You will need to pick up from a list.||You can choose the disk size during the provisioning (and can be resized) when using Standard Storage.|
|A managed disk has a predictable performance, with Standard storage (500 IOPS) or Premium storage (Depends on the disk).||Only premium storage disks have a predictable performance (depends on the disk). Standard storage has a predictable performance (500 IOPS) unless they are impacted by the Storage Account performance limits (A maximum of 40 disks per standard storage account is recommended, otherwise disks can be throttled).|
|When placing Azure Virtual Machines using managed disks under an Availability Set, disks are placed on different fault domains in order to achieve the better SLA (The Availability Set SLA is only for compute)||When placing Azure Virtual Machines using unmanaged disks under an Availability Set, there is no guarantee that the disks are placed on different fault domains, even if they are on different Storage Accounts.|
|ADE, SSE (Coming soon)||ADE, SSE|
Managed and Unmanaged Disks Pricing
Pricing of disks depends upon various factor. Usually managed disks are 3 times expensive than unmanaged disks. For exact pricing of managed disks, read this article and for Unmanaged disks, refer this article.
Azure Disks Comparison
The following table provides a comparison of Standard HDD, Standard SSD, and Premium SSD for unmanaged and managed disks to help you decide what to use.
Azure Premium Disk
Standard SSD Disk (preview)
Azure Standard HDD Disk
|Solid State Drives (SSD)||Solid State Drives (SSD)||Hard Disk Drives (HDD)|
|SSD-based high-performance, low-latency disk support for VMs running IO-intensive workloads or hosting mission critical production environment||More consistent performance and reliability than HDD. Optimized for low-IOPS workloads||HDD-based cost-effective disk for infrequent access|
|Production and performance sensitive workloads||Web servers, lightly used enterprise applications and Dev/Test||Backup, Non-critical, Infrequent access|
|P4: 32 GiB (Managed Disks only)
P6: 64 GiB (Managed Disks only)
P10: 128 GiB
P15: 256 GiB (Managed Disks only)
P20: 512 GiB
P30: 1024 GiB
P40: 2048 GiB
P50: 4095 GiB
|Managed Disks only:
E10: 128 GiB
E15: 256 GiB
E20: 512 GiB
E30: 1024 GiB
E40: 2048 GiB
E50: 4095 GiB
|Unmanaged Disks: 1 GiB – 4 TiB (4095 GiB)
Max Throughput per Disk
|250 MiB/s||Upto 60 MiB/s||Upto 60 MiB/s|
Max IOPS per Disk
|7500 IOPS||Upto 500 IOPS||Upto 500 IOPS|
Reference Article: https://docs.microsoft.com/en-us/azure/virtual-machines/windows/about-disks-and-vhds#types-of-disks
Disk Caching in Azure
A disk cache is a cache memory that is used to speed up the process of storing and accessing data from the hard disk. In Azure we have Premium Disks for Caching. Microsoft recommends to enable caching for frequently used data
Azure Disk Caching Pricing
There is no additional price for caching
Storage Tiers in Azure
There are three types of Azure disk 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 storage tier is only available at the blob level and not at the storage account level.
Reference Article: https://docs.microsoft.com/en-us/azure/storage/blobs/storage-blob-storage-tiers#overview
Conversion of HDD to SSD
We have discussed about Azure disk storage options in our last article. Today, we’ll talk about converting HDD to SSD.
To get the hassle-free migration of HDD to SSD drive done, you need to get the important prerequisites checked first. These prerequisites are mentioned below.
- You should first check whether the SSD is available in the destination region.
- Your Drive should be a Managed Disk.
- Your Size of VM should support Premium SSD if you wish to migrate to it.
- You should schedule the migration of your disks storage during a pre-existing maintenance window, as the conversion requires a restart of the VM.
Coming to the procedures conducted in PowerShell. You should be very careful when running the below mentioned commands to generate effectiveness, otherwise, you may end up making the whole procedure a liability.
You need to run Connect-AzureRmAccount in PowerShell with Azure RM module included in it to create a connection with Azure.
The following example shows how to switch a single disk of a VM from standard HDD to standard SSD, and vice versa.
# the name of the disk you want to convert
$diskName = ‘yourDiskName’
# resource group that contains the managed disk
$rgName = ‘yourResourceGroupName’
# Choose between Standard_LRS and StandardSSD_LRS based on your scenario
$storageType = ‘StandardSSD_LRS’
$disk = Get-AzureRmDisk -DiskName $diskName -ResourceGroupName $rgName
# Get parent VM resource
$vmResource = Get-AzureRmResource -ResourceId $disk.ManagedBy
# Stop and deallocate the VM before changing the storage type
Stop-AzureRmVM -ResourceGroupName $vmResource.ResourceGroupName -Name $vmResource.Name -Force
$vm = Get-AzureRmVM $vmResource.ResourceGroupName -Name $vmResource.ResourceName
# Update the storage type
$diskUpdateConfig = New-AzureRmDiskUpdateConfig -AccountType $storageType -DiskSizeGB $disk.DiskSizeGB
Update-AzureRmDisk -DiskUpdate $diskUpdateConfig -ResourceGroupName $rgName ` -DiskName $disk.Name
# Starting the Vm after successful conversion
Start-AzureRmVM -ResourceGroupName $vm.ResourceGroupName -Name $vm.Name
Reference Article: https://docs.microsoft.com/en-us/azure/virtual-machines/windows/convert-disk-storage
January 1, 2017
October 31, 2018