Unmanaged Azure Disk Snapshot functions added to AZSBTools PowerShell module to View, Add, Delete

3 new functions have been added to the AZSBTools PowerShell module to view, add, and delete snapshots of unmanaged Azure disks

The AzureRM.Compute PowerShell module (v 5.9.1 as of 1 Jan 2019) provides the Get-AzureRmSnapshotNew-AzureRmSnapshot,  and Remove-AzureRmSnapshot cmdlets to handle disk snapshots of managed disks. Although the same snapshot capabilities are available for unmanaged disks, there are no PS cmdlets to provide similar functionality for unmanaged disk snapshots.

Managed versus unmanaged disks

Managed Disks handle the storage account creation/management to avoid hitting the 20k IOPS standard storage account limit for example (no more than 40 standard disks in the same Storage Account @ 500 IOPS each). This is a pretty nice feature but it comes at a steep price. Consider Standard LRS USEast region pricing for example. A 1 TB data disk (S30) is $40.96/month

If we use 10 GB of this disk we pay $41/month even if we power off and deallocate the VM. We still pay the $41/month for this 1 TB disk including the 990 GB unused space.

In comparison, the same 1 TB unmanaged disk using the same 500 IOPS with 10 GB of used space costs $0.45/month (10 GB * $0.045 per GB).

This is because we’re billed only for the 10 GB used space not the 1023 GB allocated space, whether the VM is up and running or powered off and deallocated.

In short, managed disks come at the cost of paying for allocated space not used space. Given that used space is often as little as 1% of the allocated space, I highly recommend against using managed disks at this time (1 Jan 2019)

Well, using my own advise I find it hard to use unmanaged disks via PowerShell to perform routine Azure infrastructure management tasks such as:

  • Determine the amount of used disk space (separate post on that)
  • Manage disk snapshots; list, create, delete (the subject of this post)
  • Convert managed to unmanaged disk (separate post on that)

The functions Get-AzureRMUnmanagedDiskSnapshot, New-AzureRMUnmanagedDiskSnapshot, and Remove-AzureRMUnmanagedDiskSnapshot have been added to the AZSBTools module to simplify management of unmanaged disk snapshots via PowerShell. These functions do not affect the VM lease on its disk(s), do not require VM shutdown, and do not interfere with VM operation.


This function will list disk snapshots for a given unmanaged disk. This applies to unmanaged ARM disk snapshots only not classic ASM disks or managed ARM disks. This function depends on the AzureRM and Azure PowerShell modules available in the PowerShell Gallery. To install required module: Install-Module AzureRM, Azure 


$ParameterList = @{
    LoginName = 'sam@dmain.com'
    SubscriptionName = 'my subscription name'
    StorageAccountName = 'storfluxwidget3vm'
    ContainerName = 'vhds'
    BlobName = 'Widget3VM-20181226-093810.vhd'
Get-AzureRMUnmanagedDiskSnapshot @ParameterList

To list snapshots in a given time frame, we filter on the SnapshotTime property of the output provided by this function. This function returns objects of type Microsoft.WindowsAzure.Storage.Blob.CloudPageBlob for each snapshot found that matches the provided storageaccount/container/blob parameters. The SnapshotTime property is of type DateTimeOffset which cannot be compared directly to DateTime type. To do the required filtering/comparison, we use the [DateTimeOffset].ToLocalTime{() method as in:

Get-AzureRMUnmanagedDiskSnapshot @ParameterList | 
    where { [DateTime]$_.SnapshotTime.ToLocalTime().ToString() -GE [DateTime]'2019-01-02 8:45' }

This will list snapshots taken at or after 2 Jan 2019 8:45 (am local time)


This function will create new disk snapshot for a given unmanaged disk.


$ParameterList = @{
    LoginName = 'sam@dmain.com'
    SubscriptionName = 'my subscription name'
    StorageAccountName = 'storfluxwidget3vm'
    ContainerName = 'vhds'
    BlobName = 'Widget3VM-20181226-093810.vhd'
New-AzureRMUnmanagedDiskSnapshot @ParameterList


This function will remove one or more disk snapshots for a given unmanaged disk. In addition to the 5 parameters LoginName, SubscriptionName, StorageAccountName, ContainerName, and BlobName that this group of functions take, this function also takes 2 additional parameters; FromDate and ToDate. These 2 parameters allow us to delete snapshots taken duing a given time frame.


$ParameterList = @{
    LoginName = 'sam@dmain.com'
    SubscriptionName = 'my subscription name'
    StorageAccountName = 'storfluxwidget3vm'
    ContainerName = 'vhds'
    BlobName = 'Widget3VM-20181226-093810.vhd'
Remove-AzureRMUnmanagedDiskSnapshot @ParameterList

This deletes all disk snapshots for the provided unmanaged disk in the provided StorageAccount/Container


To use the AZSBTools PowerShell module which is available in the PowerShell Gallery, you need PowerShell 5. To view your PowerShell version, in an elevated PowerShell ISE window type


To download and install the latest version of AZSBTools from the PowerShell Gallery and its dependencies, type

Set-PSRepository -Name PSGallery -InstallationPolicy Trusted

To trust the Microsoft PowerShell Gallery repository, then

Install-Module AZSBTools,AzureRM -Force -AllowClobber

AZSBTools contains functions that depend on AzureRM modules, and they’re typically installed together.

To load the AZSBTools, and AzureRM modules type:

Import-Module AZSBTools,AzureRM -DisableNameChecking

To view a list of cmdlets/functions in AZSBTools, type

Get-Command -Module AZSBTools

To view the built-in help of one of the AZSBTools functions/cmdlets, type

help <function/cmdlet name> -show

such as

help New-SBAZServicePrincipal -show


One response

  1. Pingback: Resizing managed VM disks in Azure | Sam's Corner

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