developer1015 and welcome to the Rebex forum.
RegistryFileSystemProvider and DriveFileSystemProvider are samples that demonstrate how to write a custom file system provider.
As the sample name suggests:
1) RegistryFileSystemProvider provides access to the Windows registry.
2) DriveFileSystemProvider demonstrates how to write a simple VFS provider that uses .NET System.IO and helps developers quickly create a mental association between well-known System.IO behavior and expected VFS provider methods behavior.
If you need an Azure file storage provider, you should develop your own provider.
Your read-only provider will inherit from, well, the ReadOnlyFileSystemProvider.
Your Read/Write provider will inherit from the ReadWriteFileSystemProvider.