Cosmos: (C# Open Source Managed Operating System), an open source operating system toolkit, written in C# and some code in assembly language X# [1].

It includes an AOT compiler, IL2CPU to translate CIL (Common Intermediate Language) into native machine instructions.  Cosmos compiles user-made programs and associated libraries using IL2CPU to create a bootable native executable that can be run with no support [1]. 

The Cosmos system is used to construct storage of Microsoft's BING search engine, to handle PB level data [2]. 

Cosmos use a SQL-like scripting language called SCOPE to handle data.

Google's Map-Reduce, is corresponding to Microsoft's Dryad [2].

Bing's next-generation index-serving platform is called Tiger (similar to Cassandra of Facebook). It uses solid-state disk technology to improve Bing's search performance [4].

Microsoft Launched the public cloud service—Azure in China on May 2013, Cosmos is the key component to Azure which support the platform of public cloud.  Cosmos is a massively-parallel supercomputer comprised of tens of thousands of commodity servers, coordinating to provide vast reliable storage and stunning computation power. Every day we process hundreds of petabytes of data from Azure, Bing, AdCenter, MSN, and Windows Live. Every day we run thousands of computations that read and write petabytes of data. The underlying service needs to be unimaginably fast, and it needs to be rock-solid reliable [6][7].

[1] Cosmos (operating system)
[2] Microsoft Cosmos: Petabytes perfectly processed perfunctorily
[3] Cosmos: Big Data and Big Challenges, by Pat Helland, July 2011 (PDF)
[4] The Bing back-end: More on Cosmos, Tiger and Scope
[5] microsoft cosmos scope jobs
[6] Senior Software Development Engineer (SDE) for Cloud Platform Job
[7] Jobs in IT: Geek Out with Hot Tech Jobs at Cosmos