Is Microsoft's Cloud OS actually a Cloud DB?

What, exactly, is Microsoft's Cloud OS? Is it an operating system (OS) at all? Or is more of a database (or two) in the Blue/CloudDB sky?

Microsoft officials have used "Cloud OS" as shorthand to refer to the Windows Live Core, or the platform that will power Microsoft's current and forthcoming datacenter-based family of services.

But what, exactly, is Microsoft's Cloud OS? Is it an operating system (OS) at all?

Microsoft officials have used the "Cloud OS" nomenclature to refer to Microsoft's services platform. But more recently, Microsoft -- like archrival Google -- is starting to attempt to backtrack, claiming that there is no such thing as a Cloud OS.

Obviously, there is something substantial under development by the Microsoft all-star Windows Live Core team. (You don't put folks like Windows NT father Dave Cutler on a team if it has small ambitions.)

Microsoft officials have declined repeated questions about what the Windows Live Core is, other than to say it is a platform for running current and future services.

Fortunately, other sources in and around the company aren't quite so gun-shy. Based on various comments by sources who've requested anonymity, here's my best attempt at piecing together Microsoft's evolving cloud strategy.

First off, from what I am hearing, Cloud OS is a project that Microsoft is planning to deliver in phases. Currently, Microsoft's expanding family of datacenter servers that power its various Windows Live, Office Live and other online services are running Windows Server.

In the initial phases of its Cloud OS rollout, sources say, Microsoft is looking to build atop Windows Server and create a distributed technology layer, or platform, that will handle the back-end chores required by users, partners and service providers.

There are a number of elements of this distributed layer, my sources claim, including at least two different databases. One of these is known as the Cloud database; the other as Blue/Cloud. CloudDB is a file-system-based storage system, sources say; Blue is a hosted version of SQL Server under development by the SQL Server team, they claim. Microsoft is planning to roll out Blue to a very limited set of customers/partners, starting in 2008, the sources say. From what I can tell, "Blue" also seems to refer to the query processor that builds on top of the cheap, file-system-based storage enabled by CloudDB.

(Microsoft also is known to be working on one or more Live storage service(s), that will allow users to store their photos, videos and other data "in the cloud." But this is different from the CloudDB itself.)

Then there is another component in Microsoft's Cloud mix that is code-named "Velocity," which is some kind of distributed application cache designed to improve performance by providing query-processing capabilities across application data. Microsoft's "Harmonica" data-synchronization technology that will allow users to sync information across devices, client-/server-based applications and "the cloud" also seems to fit into the picture, too. (Harmonica, from the little I've heard about that SQL Server team project, is an outgrowth of Microsoft's WinFS Windows File System that the company decided to cut from Vista and Longhorn Server and fold back into the SQL Server team.)

The ultimate goal of Microsoft's Cloud OS team, according to my sources, is to create a distributed network of microkernel-based operating systems. Yes, that does seem to mean that the team's end game is to write a new distributed operating system from scratch. I have absolutely no idea of the tentative timing of such a beast, but I'm sure the due date is likely to be cloudy.

Again, just to be clear: None of this information is confirmed by Microsoft. I'm just trying to fit together the puzzle pieces about which information is starting to circulate.

Anyone have additional details/guesses that might fill in some of the gaps?