SQL Server 2012 PDW uses the new updateable version of xVelocity columnstore capabilities as a part of PDW for added linear scale out.
This is a memory-optimized columnstore index, which is both updateable and clustered. In the standard SQL Server 2012 Database Engine, columnstore indexes don’t allow table updates to tables with columnstore indexes.
By reorienting data in a column format rather than a traditional row store, you can get up to 50 times the performance gains. This is due to the grouping of data into a columnar format, which contains values from multiple rows. The net effect is much higher efficiency in both storage and the dataset processing of column-oriented SQL queries.