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Uploading and Downloading VHDs to Windows Azure

One of the great features of Windows Azure is VHD mobility. Simply put it means you can upload and download VHDs to and from the cloud.


Technical Notes

A few things to point out while I’m here. Currently, Windows Azure only supports the VHD file format in a fixed disk format.
That being said the Add-AzureVHD cmdlet supports converting a dynamic VHD on upload to a fixed VHD so you do not have to worry about converting them up front.

Also, both the Add-AzureVHD and Save-AzureVHD cmdlets have intrinsic knowledge of the VHD file format and during upload or download only copy the written bytes and skip the empty. This is a huge optimization!

So let’s jump right in using PowerShell. This page assumes your PowerShell client is already setup to access your Windows Azure subscription. If this is not the case read through the Getting Started with Windows Azure PowerShell Cmdlets first.

Uploading a VHD

import-module azure
select-azuresubscription "mysubscriptionname"
 
$sourceVHD = "D:StorageDemosmyvhd.vhd"
$destinationVHD = "https://mwwestus1.blob.core.windows.net/uploads/myvhd.vhd"
 
Add-AzureVhd -LocalFilePath $sourceVHD -Destination $destinationVHD `
             -NumberOfUploaderThreads 5

As you can see the code to upload a VHD to your Windows Azure Storage Account is pretty simple.

To make the VHD usable you need to register it with Windows Azure.

Register VHD as a Data Disk

# Register as a plan old data disk 
Add-AzureDisk -DiskName 'mydatadisk' -MediaLocation $destinationVHD `
               -Label 'mydatadisk'

When the code above is run the uploaded VHD will be registered in Windows Azure as a data disk named ‘mydatadisk’. Refresh the portal and you will see it in the Disks list and it will also be available for attaching to a virtual machine.

If you are uploading a VHD with an operating system on it you need to tell that to Windows Azure.

Register VHD as an OS Disk

This code registers the disk as bootable. Meaning you can now create a virtual machine and specify this disk as the boot disk.

# Register as a plan old data disk 
Add-AzureDisk -DiskName 'myosdisk' -MediaLocation $destinationVHD `
               -Label 'myosdisk' -OS Windows # or Linux

Creating a VM from uploaded VHDs

As I mentioned above you can specify a disk to boot from instead of provisioning from an image. The PowerShell code to do so is simple. You can of course add disks and endpoints in between New-AzureVMConfig and New-AzureVM as well.

New-AzureVMConfig -DiskName 'myosdisk' -Name 'myvm1' -InstanceSize Small | 
    Add-AzureDataDisk -Import -DiskName 'mydatadisk' -LUN 0 |
    New-AzureVM -ServiceName 'mycloudsvc' -Location 'West US'

Now that you have seen how to upload VHD’s to the cloud let’s walk through the equally simple download process.

Downloading a VHD from Windows Azure

The same pattern as Add-AzureVHD just reversed!

select-azuresubscription "mysubscriptionname"
 
$sourceVHD = "https://mwwestus1.blob.core.windows.net/uploads/mydatadisk.vhd"
$destinationVHD = "D:StorageDemosmydatadisk-downloaded.vhd"
 
Save-AzureVhd -Source $sourceVHD -LocalFilePath $destinationVHD `
             -NumberOfThreads 5

That’s it! Uploading and downloading VHDs to Windows Azure is fast and simple

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