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.VERSION 1.0.0
.GUID e009159d-97e2-492a-a289-42426518dd41
.AUTHOR Arjun Bahree
.COPYRIGHT (c) 2018 Arjun Bahree. All rights reserved.
.TAGS Windows PowerShell DiskPartition OSDisk
Lets you extend/Increase the OS Drive Partition Size for any Windows based Machine.
Lets you extend/Increase the OS Drive Partition Size for any Windows based Machine.
This script lets you extend/Increase the OS Drive Partition size for any Windows based Machine by adding the entire
unallocated space available on the OS Disk, if any. This script is particularly useful for extending the OS Drive
partition for Windows based Azure VM's, after the VM OS Disk size has been Increased from outside the VM using
PowerShell or Azure Portal. This is so because the Increase in size done for the VM OS Disk from outside does not
automatically get added to the OS Drive partition, and shows as unallocated space on the OS Disk of the VM. You will
have to manually extend the OS Drive partition from within the VM OS to add the unallocated space to the OS
partition. This script helps to automate the same process end-to-end. You need to be already logged into your Azure
account through PowerShell before calling this script.
Author: Arjun Bahree
Creation Date: 28/Dec/2017
Last Revision Date: 28/Dec/2017
Development Environment: VS Code IDE
PS Version: 5.1
Platform: Windows
param ()
# Iterate through all the disks on the Windows machine
foreach($disk in Get-Disk)
# Check if the disk in context is a Boot and System disk
if((Get-Disk -Number $disk.number).IsBoot -And (Get-Disk -Number $disk.number).IsSystem)
# Get the drive letter assigned to the disk partition where OS is installed
$driveLetter = (Get-Partition -DiskNumber $disk.Number | where {$_.DriveLetter}).DriveLetter
Write-verbose "Current OS Drive: $driveLetter :\"
# Get current size of the OS parition on the Disk
$currentOSDiskSize = (Get-Partition -DriveLetter $driveLetter).Size
Write-verbose "Current OS Partition Size: $currentOSDiskSize"
# Get Partition Number of the OS partition on the Disk
$partitionNum = (Get-Partition -DriveLetter $driveLetter).PartitionNumber
Write-verbose "Current OS Partition Number: $partitionNum"
# Get the available unallocated disk space size
$unallocatedDiskSize = (Get-Disk -Number $disk.number).LargestFreeExtent
Write-verbose "Total Unallocated Space Available: $unallocatedDiskSize"
# Get the max allowed size for the OS Partition on the disk
$allowedSize = (Get-PartitionSupportedSize -DiskNumber $disk.Number -PartitionNumber $partitionNum).SizeMax
Write-verbose "Total Partition Size allowed: $allowedSize"
if ($unallocatedDiskSize -gt 0 -And $unallocatedDiskSize -le $allowedSize)
$totalDiskSize = $allowedSize
# Resize the OS Partition to Include the entire Unallocated disk space
$resizeOp = Resize-Partition -DriveLetter C -Size $totalDiskSize
Write-verbose "OS Drive Resize Completed $resizeOp"
else {
Write-Verbose "There is no Unallocated space to extend OS Drive Partition size"