Windows® Internals, Sixth Edition, Part 1

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Windows Server 2008 R2 Datacenter

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Windows Server 2008 R2 for Itanium-Based Systems

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Although there are several client and server retail packages of the Windows operating system, they share a common set of core system files, including the kernel image, Ntoskrnl.exe (and the PAE version, Ntkrnlpa.exe); the HAL libraries; the device drivers; and the base system utilities and DLLs. These files are identical for all editions of Windows 7 and Windows Server 2008 R2.

With so many different editions of Windows and each having the same kernel image, how does the system know which edition is booted? By querying the registry values ProductType and ProductSuite under the HKLM\SYSTEM\CurrentControlSet\Control\ProductOptions key. ProductType is used to distinguish whether the system is a client system or a server system (of any flavor). These values are loaded into the registry based on the licensing policy file described earlier. The valid values are listed in Table 2-3. This can be queried from the user-mode GetVersionEx function or from a device driver using the kernel-mode support function RtlGetVersion.

Table 2-3. ProductType Registry Values

Edition of Windows

Value of ProductType

Windows client

WinNT

Windows server (domain controller)

LanmanNT

Windows server (server only)

ServerNT

A different registry value, ProductPolicy, contains a cached copy of the data inside the tokens.dat file, which differentiates between the editions of Windows and the features that they enable.

If user programs need to determine which edition of Windows is running, they can call the Windows VerifyVersionInfo function, documented in the Windows Software Development Kit (SDK). Device drivers can call the kernel-mode function RtlVerifyVersionInfo, documented in the WDK.

So if the core files are essentially the same for the client and server versions, how do the systems differ in operation? In short, server systems are optimized by default for system throughput as high-performance application servers, whereas the client version (although it has server capabilities) is optimized for response time for interactive desktop use. For example, based on the product type, several resource allocation decisions are made differently at system boot time, such as the size and number of operating system heaps (or pools), the number of internal system worker threads, and the size of the system data cache. Also, run-time policy decisions, such as the way the memory manager trades off system and process memory demands, differ between the server and client editions. Even some thread scheduling details have different default behavior in the two families (the default length of the time slice, or thread quantum—see Chapter 5 for details). Where there are significant operational differences in the two products, these are highlighted in the pertinent chapters throughout the rest of this book. Unless otherwise noted, everything in this book applies to both the client and server versions.

EXPERIMENT: Determining Features Enabled by Licensing Policy

As mentioned earlier, Windows supports more than 100 different features that can be enabled through the software licensing mechanism. These policy settings determine the various differences not only between a client and server installation, but also between each edition (or SKU) of the operating system, such as BitLocker support (available on Windows server as well as the Ultimate and Enterprise editions of Windows client). You can use the SlPolicy tool available from Winsider Seminars & Solutions (www.winsiderss.com/tools/slpolicy.htm) to display these policy values on your machine.

Policy settings are organized by a facility, which represents the owner module for which the policy applies. You can display a list of all facilities on your system by running Slpolicy.exe with the –f switch:C:\>SlPolicy.exe -f SlPolicy v1.05 - Show Software Licensing Policies Copyright (C) 2008-2011 Winsider Seminars & Solutions Inc. www.winsiderss.com Software Licensing Facilities: Kernel Licensing and Activation Core DWM SMB IIS . . .