Test drive: SQL Server 2012
SQL Server 2012’s biggest new feature for enterprises is called AlwaysOn and is a new approach to high availability. You can specify up to four secondary replicas within an availability group, which can be within a datacenter or across datacenters. Secondary replicas are not idle, but can be used for backup, reporting and queries in order to make efficient use of hardware.
DB-MIRROR is part of the new Always-On feature, designed to simplify database mirroring via a management tools wizard.
Another scalability enhancement is ColumnStore indexes. This is for data warehouses, and indexes each column in a separate set of disk pages rather than storing multiple rows per page. If your query requests only a few columns from a table, this is far more efficient, and Microsoft claims performance improvements of hundreds-fold for large datasets that do not fit in RAM, and from six to 10-fold improvements in cases where the working set does fit in RAM.