What is the Windows Azure Drive?
The Windows Azure Drive allows Windows Azure applications to mount a Page Blob, which is a single volume NTFS VHD. All writes in the application are made durable to the blob, and reads come out of the local VM cache or the page blob if there is a cache miss. This allows applications to upload/download VHDs via blobs, and the VHD is durable and survives the failover of the VM, since it is backed by a paged blob.