Microsoft Big Data stack
Microsoft is working aggressively towards bridging some of the gaps in its stack for Big Data processing and has a few announcements towards this in recent past.
Here is a view covering various MS technologies for structured and un-structured data analysis.

Apache Hadoop based platform support
Microsoft also has announced Apache Hadoop based distribution with Windows Server and Windows Azure which is expected to be available in CY12 (most probably in late second half). This is for customers who have already adopted open source Apache Hadoop based solutions but would like to run on bespoke Microsoft and intends to integrate best of the two. Check this here
LINQ TO HPC
LINQ to HPC erstwhile Dryad from Microsoft Research, is a distributed runtime for processing un-structured data and runs on top of Windows Server 2008 R2 cluster having HPC pack.
LINQ to HPC is now shipped with Windows Server 2008 R2 SP3 HPC pack. This is currently in RC (Release candidate) and is expected to be released in early 2011. The RC bits can be downloaded from here
LINQ to HPC based unstructured data analysis is recommended for customers who would like to utilize existing .NET skills and environment in the enterprise.
Daytona
Daytona is a runtime that needs to be installed on Windows Azure and provides the execution environment for running large computing jobs. Daytona supports HPC scenarios for data analytics, financial analysis, machine learning on Windows Azure. It is currently in beta and expected to be available in early 2012.
Other existing products
SQL Server Parallel DataWarehouse (PDW) is an appliance meant for large scale data warehousing, BI needs.
SQL Server 2008, or SQL Server 2012 (beta) provides BI stack for standard BI, DW needs
• SQL Server Analysis Services is part of SQL Server, as well PDW and supports cube for (OLAP) Online Analyticalprocessing.
• SQL Server Integration Services (SSIS) is part of SQL Server, as well PDW and provides data integration, cleansing, etc. capability
• SQL Server Reporting Services (SSRS) is part of SQL Server, as well PDW and provides data reporting, slicing, dicing, etc.
• SQL Server also provides data mining algorithms.
• ExcelDataScope is a reporting layer from Microsoft Research and is yet to be released.More about it here
These are some of the key technologies already released and slated to release in evolving MS Big Data stack.


