What's New in Hyper-V in Windows Server 2008 R2

What are the major changes?

The Hyper-V™ role enables you to create and manage a virtualized server computing environment by using a technology that is part of Windows Server® 2008 R2. The improvements to Hyper-V include new live migration functionality, support for dynamic virtual machine storage, and enhancements to processor and networking support.
The following changes are available in Windows Server 2008 R2:

• Live migration
  
• Dynamic virtual machine storage
  
• Enhanced processor support
  
• Enhanced networking support
  

What does Hyper-V do?

Hyper-V is a role in Windows Server 2008 R2 that provides you with the tools and services you can use to create a virtualized server computing environment. This virtualized environment can be used to address a variety of business goals aimed at improving efficiency and reducing costs. This type of environment is useful because you can create and manage virtual machines, which allows you to run multiple operating systems on one physical computer and isolate the operating systems from each other.

Who will be interested in this feature?

The Hyper-V role is used by IT professionals who need to create a virtualized server computing environment.

What new functionality does Hyper-V provide?

Improvements to Hyper-V include new live migration functionality.

Live migration

Live migration allows you to transparently move running virtual machines from one node of the failover cluster to another node in the same cluster without a dropped network connection or perceived downtime. Live migration requires the failover clustering role to be added and configured on the servers running Hyper-V. In addition, failover clustering requires shared storage for the cluster nodes. This can include an iSCSI or Fiber-Channel Storage Area Network (SAN). All virtual machines are stored in the shared storage area, and the running virtual machine state is managed by one of the nodes.
On a given server running Hyper-V, only one live migration (to or from the server) can be in progress at a given time. This means that you cannot use live migration to move multiple virtual machines simultaneously.
We recommend using the new Cluster Shared Volumes (CSV) feature of Failover Clustering in Windows Server 2008 R2 with live migration. CSV provides increased reliability when used with live migration and virtual machines, and also provides a single, consistent file namespace so that all servers running Windows Server 2008 R2 see the same storage.

Why is this change important?

Live migration does the following to facilitate greater flexibility and value:

• Provides better agility. Datacenters with multiple servers running Hyper-V can move running virtual machines to the best physical computer for performance, scaling, or optimal consolidation without affecting users.
  
• Reduces costs. Datacenters with multiple servers running Hyper-V can service their servers without causing virtual machine downtime or the need to schedule a maintenance window. Datacenters will also be able to reduce power consumption by dynamically increasing consolidation ratios and turning off unused servers during times of lower demand.
  
• Increases productivity. It is possible to keep virtual machines online, even during maintenance, which increases productivity for both users and server administrators.
  

Are there any dependencies?

Live migration requires the failover clustering role to be added and configured on the servers running Hyper-V.

What existing functionality is changing?

The following list briefly summarizes the improvements to existing functionality in Hyper-V:

• Dynamic virtual machine storage. Improvements to virtual machine storage include support for hot plug-in and hot removal of the storage on a SCSI controller of the virtual machine. By supporting the addition or removal of virtual hard disks and physical disks while a virtual machine is running, it is possible to quickly reconfigure virtual machines to meet changing requirements. Hot plug-in and removal of storage requires the installation of Hyper-V integration services (included in Windows Server 2008 R2) on the guest operating system.
  
• Enhanced processor support. You can now have up to 64 physical processor cores. The increased processor support makes it possible to run even more demanding workloads on a single host. In addition, there is support for Second-Level Address Translation (SLAT) and CPU Core Parking. CPU Core Parking enables Windows and Hyper-V to consolidate processing onto the fewest number of possible processor cores, and suspends inactive processor cores. SLAT adds a second level of paging below the architectural x86/x64 paging tables in x86/x64 processors. It provides an indirection layer from virtual machine memory access to the physical memory access. In virtualization scenarios, hardware-based SLAT support improves performance. On Itanium-based processors, this is called Extended Page Tables (EPT), and on AMD-based processors, it is called Nested Page Tables (NPT).
  
• Enhanced networking support. Support for jumbo frames, which was previously available in nonvirtual environments, has been extended to be available on virtual machines. This feature enables virtual machines to use jumbo frames up to 9,014 bytes in size, if the underlying physical network supports it.