This is within the 32Gb Azure Disk size so will work in this scenario. So if we set the OS partition to 31GB and add 500MB for the System Reserved partition we get 31.5Gb in total for Disk0. Work out what the new OS Volume size will be + the existing System Reserved partition. We now have the PartitionNumber which is “2” – this is the OS Disk “C” Run: Get-Partition -DiskNumber 0 where 0 is the Disk number of the OS Disk: We can see that there is sufficient space on the C drive to reduce the Azure Managed disk size to 32Gb: As the disk is Managed, we will be charged for a 128GB disk: In this example, the Azure VM AAHW2 ( yeah I know you can see I’ve done a bad job of masking the first few chars of the original name) has a managed OS disk size of 100Gb running the Standard HDD storage type. The technique used to the reduce the disk in this post is identical to that of the Microsoft post mentioned above, except that here we use only PowerShell without relying on an opensource tool.Īnother difference in my method is that it is dynamic - in that it reads the footer from a new disk created in Azure, ensuring the correct value is always written and up to date.įinally, I am using the swap disk method rather than creating a new VM from the new Managed Disk Shrink Disk Pre-Reqs If you find there is plenty of free space to go down to a 64GB or even a 32GB OS Disk, then check out these steps. Many on-prem VMs are built from a VMWare template, often with an oversized OS drive to cater for growth which never materialises. This is an adapted version of my original post Shrink Azure VM OS disk size (reduce) Scenarioįor cost saving (and performance) reasons you may want to reduce the size of the OS Disk (or data disks for that fact) that are already assigned to a running VM - if there is sufficient space within the volume to first shrink the volume within the OS. A Microsoft blog post covers this statement and also an alternative approach to this post. Using PowerShell (and the Azure Portal) to reduce/shrink the OS Managed Disk size for a Windows VM in Azure.Īt present it is not supported to reduce/shrink the OS disk (managed or unmanaged) size of an Azure VM from the Azure Portal (say from 128Gb to 32Gb for example), using PowerShell or any other tools.

Azure disk snapshot