Windows Server Core Architecture

The architecture of Windows Server Core is extremely similar to a full installation of Windows Server 2008. Windows Server Core uses the same device drivers, has the same kernel installed on disk, and behaves the same as a full installation of Windows Server. The main difference is that the graphical subsystem of Windows, as well as the .NET Framework and other products nd services, are absent from a Core installation. This means that any application that relies on any of those pieces of functionality won’t run, such as websites that rely on the ASP.NET framework. Some applications, such as SQL Server 2008, also won’t work on a Windows Server 2008 Core installation. Additionally, items such as Internet Explorer and Windows Mail have been removed.


Benefits
Windows Server Core offers a number of benefits, regardless of its intended use:

Reduced maintenance. By default, a Windows Server Core system has very few binaries installed. When a role is added, only the components that are necessary for the role are installed. The binaries are still present on the system, which allows for those components to be updated during normal patch cycles. No longer will your Windows Servers need updates for little-used components. Systems running Windows Server Core can see up to 40 percent fewer patches compared to systems running Windows Server 2003.

Reduced attack surface. Because fewer applications and services are running on the server, there are fewer avenues to exploit. Exploits aimed at components that don’t exist on the server don’t get a chance to work.

Reduced management. Because fewer components are installed on the system, there’s less administrative overhead.

Less disk space required. Fewer binaries being installed on disk mean that less disk space is required. Windows Server Core requires only 10GB of disk space, as opposed to 20GB for a full installation of Windows Server 2008.



Disadvantages
Although the Server Core installation option sounds great in theory, administrators need to be aware of the following concerns:

Remote management. Because Windows Server Core provides no local GUI-based administration tools, you perform the bulk of administration for the system from another system with a full installation of Windows Server 2008 or enterprise-management tools. Many of the Windows administration tools that are accessed through the Microsoft Management Console (MMC) can be configured to administer other computers in either a workgroup or a domain setting.


Command line. The only interface presented at a console or remote logon at a Windows Server Core system is the command line. For some administrators, that’s preferred—and those administrators probably use batch files (.BAT) and command scripts (.CMD) to perform mundane administration tasks. Not all administrators prefer that approach, however.

No PowerShell. Because Windows Server Core doesn’t include the .NET Framework, the PowerShell feature isn’t available. You can still use PowerShell from another system to perform administrative tasks against the Windows Server Core system via Windows Management Interface (WMI).

Inability to transition from Core to full. A Windows Server Core installation can’t be “upgraded” to a full installation of Windows Server. To move to a full installation of Windows Server 2008, you must reinstall the system.

Source of Information : Sybex Windows Server 2008 Hyper-V Insiders Guide to Microsofts Hypervisor