ISCSI Target Server is a feature that lets administrators boot multiple computers on a network from a single operating system image that's stored in a central location. iSCSI Target Server has the ability to boot hundreds of computers using just a single OS image.
The software for iSCSI Target Server is bundled with the Windows Server 2012 software and can be cluster aware. Microsoft says there are a number of common situations in which iSCSI Target Server can be a useful option for enterprises. ISCSI Target Server, for example, can help applications by providing continuously available block storage. It can also support iSCSI initiators that are not from Microsoft, which can help with shared storage in a mixed software environment.
ISCSI Target Server received a few functionality updates with the release of Windows Server 2012 R2, improving scalability, manageability and better optimization for caching at the disk-level.