Attach a data disk to a Windows VM with PowerShell

Applies to: ✔️ Windows VMs ✔️ Flexible scale sets

This article shows you how to attach both new and existing disks to a Windows virtual machine by using PowerShell.

First, review these tips:

• The size of the virtual machine controls how many data disks you can attach. For more information, see Sizes for virtual machines.
• To use premium SSDs, you'll need a premium storage-enabled VM type, like the DS-series virtual machine.

Lower latency

In select regions, the disk attach latency has been reduced, so you'll see an improvement of up to 15%. This is useful if you have planned/unplanned failovers between VMs, you're scaling your workload, or are running a high scale stateful workload such as Azure Kubernetes Service. However, this improvement is limited to the explicit disk attach command, Add-AzVMDataDisk. You won't see the performance improvement if you call a command that may implicitly perform an attach, like Update-AzVM. You don't need to take any action other than calling the explicit attach command to see this improvement.

Add an empty data disk to a virtual machine

This example shows how to add an empty data disk to an existing virtual machine.

Using managed disks

$rgName = 'myResourceGroup'
$vmName = 'myVM'
$location = 'China East'
$storageType = 'Premium_LRS'
$dataDiskName = $vmName + '_datadisk1'

$diskConfig = New-AzDiskConfig -SkuName $storageType -Location $location -CreateOption Empty -DiskSizeGB 128
$dataDisk1 = New-AzDisk -DiskName $dataDiskName -Disk $diskConfig -ResourceGroupName $rgName

$vm = Get-AzVM -Name $vmName -ResourceGroupName $rgName
$vm = Add-AzVMDataDisk -VM $vm -Name $dataDiskName -CreateOption Attach -ManagedDiskId $dataDisk1.Id -Lun 1

Update-AzVM -VM $vm -ResourceGroupName $rgName

Using managed disks in an Availability Zone

To create a disk in an Availability Zone, use New-AzDiskConfig with the -Zone parameter. The following example creates a disk in zone 1.

$rgName = 'myResourceGroup'
$vmName = 'myVM'
$location = 'China North 3'
$storageType = 'Premium_LRS'
$dataDiskName = $vmName + '_datadisk1'

$diskConfig = New-AzDiskConfig -SkuName $storageType -Location $location -CreateOption Empty -DiskSizeGB 128 -Zone 1
$dataDisk1 = New-AzDisk -DiskName $dataDiskName -Disk $diskConfig -ResourceGroupName $rgName

$vm = Get-AzVM -Name $vmName -ResourceGroupName $rgName
$vm = Add-AzVMDataDisk -VM $vm -Name $dataDiskName -CreateOption Attach -ManagedDiskId $dataDisk1.Id -Lun 1

Update-AzVM -VM $vm -ResourceGroupName $rgName

Initialize the disk

After you add an empty disk, you'll need to initialize it. To initialize the disk, you can sign in to a VM and use disk management. If you enabled WinRM and a certificate on the VM when you created it, you can use remote PowerShell to initialize the disk. You can also use a custom script extension:

$location = "location-name"
$scriptName = "script-name"
$fileName = "script-file-name"
Set-AzVMCustomScriptExtension -ResourceGroupName $rgName -Location $locName -VMName $vmName -Name $scriptName -TypeHandlerVersion "1.4" -StorageAccountName "mystore1" -StorageAccountKey "primary-key" -FileName $fileName -ContainerName "scripts"

The script file can contain code to initialize the disks, for example:

$disks = Get-Disk | Where partitionstyle -eq 'raw' | sort number

$letters = 70..89 | ForEach-Object { [char]$_ }
$count = 0
$labels = "data1","data2"

foreach ($disk in $disks) {
    $driveLetter = $letters[$count].ToString()
    $disk |
    Initialize-Disk -PartitionStyle MBR -PassThru |
    New-Partition -UseMaximumSize -DriveLetter $driveLetter |
    Format-Volume -FileSystem NTFS -NewFileSystemLabel $labels[$count] -Confirm:$false -Force
    $count++
}

Attach an existing data disk to a VM

You can attach an existing managed disk to a VM as a data disk.

$rgName = "myResourceGroup"
$vmName = "myVM"
$dataDiskName = "myDisk"
$disk = Get-AzDisk -ResourceGroupName $rgName -DiskName $dataDiskName

$vm = Get-AzVM -Name $vmName -ResourceGroupName $rgName

$vm = Add-AzVMDataDisk -CreateOption Attach -Lun 0 -VM $vm -ManagedDiskId $disk.Id

Update-AzVM -VM $vm -ResourceGroupName $rgName

Next steps

You can also deploy managed disks using templates. For more information, see Using Managed Disks in Azure Resource Manager Templates or the quickstart template for deploying multiple data disks.