Inside Windows Server 2008 R2

Although it seems hard to believe, the next release of Microsoft's server OS, Windows Server 2008 R2, is right around the corner. At press time, Server 2008 R2 was in beta and scheduled for release late this year. Let's dive in and take a look at some of the most important new features in Server 2008 R2.

The Exclusive 64-Bit Club
Server 2008 R2 is the first Microsoft Windows Server OS to take the 64-bit–only road. This enhancement shouldn't be a problem for new installations, because most of today's servers are x64 compatible. However, Server 2008 R2 won't run on older 32-bit servers. Existing 32-bit applications can run on Server 2008 R2 by using the OS's 32-bit compatible Windows-On-Windows (WoW) subsystem.

In addition to going 64-bit–only, Server 2008 R2 also benefits from scalability enhancements. Server 2008 R2 can address as many as 256 logical processors on one server—up from a maximum of 64 in the original Windows Server 2008 release.

New Hyper-V Release
Another important enhancement in Server 2008 R2 is the inclusion of a new release of Hyper-V. A prerelease version of Hyper-V was shipped with the original Server 2008, then the final release was added as an update. The Server 2008 R2 version of Hyper-V can use more than 32 logical processors on the host virtual machine (VM). This new Hyper-V release can take advantage of the latest Intel and AMD Second Level Address Translation (SLAT) hardware virtualization support. SLAT lets the hypervisor dispense with shadow page tables and handles the translation of VM memory to physical memory, resulting in improved VM performance. Hyper-V in Server 2008 R2 also increases the memory support for VMs to 64GB. TCP offload and jumbo frames provide improved networking performance. Another enhancement to Hyper-V in Server 2008 R2 is enhanced support for PowerShell management via a set of dedicated cmdlets. However, the single most important feature in Server 2008 R2 related to virtualization is support for Live Migration.

Live Migration
Live Migration is Microsoft's answer to VMware's VMotion. Live Migration lets you move Hyper-V VMs between Server 2008 R2 hosts with no downtime. Like VMotion, Live Migration allows the administrator to handle planned downtime scenarios with no loss of VM availability. Live Migration requires Windows Failover Clustering and leverages Windows Clustering Services and the new Cluster Shared Volumes technology to move VMs between hosts in milliseconds. Server 2008 R2's new Cluster Shared Volumes technology lets multiple cluster nodes concurrently access the same LUN, which in turn lets them access the same Virtual Hard Disks (VHDs). Thus, the VHDs don't need to be physically moved to perform a Live Migration. Figure 1 shows an overview of how Live Migration works.

To perform a Live Migration, the administrator initiates the migration of a VM from the source node to a target cluster node. Live Migration creates a container VM on the target node. You don't need to move the VHD, because Cluster Shared Volumes gives the target node full access to the VHD file stored on the SAN. Next, the source VM's current memory is copied to the target node. Clients connected to the source VM continue to run, and all the changed memory pages in the source VM are mirrored. The mirrored pages are then copied to the target VM until the delta is zero or until a finite number of iterations are reached. At that point Live Migration pauses the VM on the source, copies any remaining dirty pages, copies the partition state, starts the VM on the target node, and redirects all of the client connections from the source VM to the target VM. The migration is then complete and the source VM is deleted.

Active Directory Enhancements
From a Windows administrator's perspective, the biggest change in Server 2008 R2 is undoubtedly the new Active Directory Administrative Center. The ADAC provides a brand-new task-driven interface for managing Active Directory (AD). The older Users and Computers, Site and Services, and Domains and Trusts options still exist; however, the new ADAC's task-driven interface provides a better way to handle day-to-day tasks such as working with users, computers, groups, and organization units (OUs). The ADAC is installed when you run Dcpromo to make a Server 2008 R2 system a domain controller (DC). Figure 2 shows the new ADAC.

As you can see in Figure 2, the ADAC provides breadcrumb-style navigation much like Windows Explorer. By default, the ADAC navigation pane on the left side of the screen uses either a treeview or a simple list view. However, you can also customize the view by adding commonly used containers to the navigation pane. The new ADAC can open AD using a different set of credentials than your logon credentials. It can also manage AD objects across multiple domains. The current version of the ADAC runs only on Server 2008 R2. Future versions of Windows 7 will also be able to run the ADAC. For more information about the ADAC, see the Microsoft TechNet article "What's New in AD DS: Active Directory Administrative Center."