Quite often people want to use the D: drive in a Windows Azure VM for their apps or data. For example, you might want to migrate an existing Windows application to the cloud without change and this app is relying on data being stored on the D: drive. Or your corporate policy mandates installing applications on D:.
By default, Windows VMs in Windows Azure host their operating system on drive C: as a persistent data disk located in blob storage. Additionally, each VM gets a scratch disk labeled as D: which is NOT persisted in blob storage. It’s rather disk space provided by the specific Hyper-V host of your VM. Data on this scratch disk is volatile in a sense that it will get lost whenever your VM will be relocated to another physical host (e.g. because you changed the VM size in the portal).
So if you want to use D: as a persistent data disk, read on…