Creating and using a blob snapshot
The Windows Azure Blob Service supports the creation of read-only snapshots of a blob. A storage account is billed only for those blocks and pages in a snapshot that differ from those in the underlying blob. A blob snapshot is useful in providing a backup for a blob as it can be used to reset the blob to an earlier state. Indeed, multiple snapshots can be made over time allowing a historic record to be kept of changes to a blob.
An important use case for blob snapshots is provided by the Azure Drive feature. An Azure Drive is a page blob comprising an NTFS-formatted VHD that can be attached to a hosted service role instance and accessed as an NTFS drive. To avoid read-write conflicts, a single VHD page blob can be attached to only one instance at a time. However, a blob snapshot is read-only, allowing no possibility of write contention, so an arbitrary number of instances can attach a VHD snapshot simultaneously.
A blob snapshot is created using the CloudBlob...
