Microsoft WINDOWS SERVER 2008 R2 WHITE PAPER

Windows Server 2008 R2 Hyper-V™ Live Migration

White Paper

Published: August 09

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Table of Contents

Business Value of Windows Server 2008 R2 Hyper-V™ and Live Migration ................................................. 3

Overview of Windows Server 2008 R2 Hyper-V™ Features.......................................................................... 4

Dynamic VM storage ............................................................................................................................. 4

Enhanced Processor Support ................................................................................................................ 4

Enhanced Networking Support ............................................................................................................. 5

Cluster Shared Volumes (CSV) .............................................................................................................. 5

Live Migration ....................................................................................................................................... 5

Live Migration Overview ........................................................................................................................... 5

Live Migration Compared to Quick Migration ...................................................................................... 6

Live Migration Architecture ...................................................................................................................... 6

Requirements ........................................................................................................................................ 7

Live Migration Scenarios ......................................................................................................................... 13

Physical Computer Maintenance ........................................................................................................ 13

Dynamic Datacenter ........................................................................................................................... 15

Green IT ............................................................................................................................................... 16

Deploying Live Migration ........................................................................................................................ 17

Managing Live Migration ........................................................................................................................ 18

Summary ..................................................................................................................................................... 18

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Business Value of Windows Server 2008 R2 Hyper-V™

For More Information:

http://www.microsoft.com/windowsserver2008/en/us/hyperv-R2.aspx

“We expect to consolidate an

additional 75 servers using Hyper-V, which will lead to a cost savings of more than $325,000 annually. By the time we hit our fifth virtual

machine, we’ve usually paid

for the host. Long term, we will be able to reduce our total data center holdings by 75 percent—from nearly 400 servers to fewer than 100 servers.”

-Robert McShinsky, Senior Systems Administrator Dartmouth-Hitchcock Medical Center

and Live Migration

Today’s IT departments are under increasing pressure to manage and support expanding computer

resources while at the same time reducing costs. Server virtualization, which lets multiple operating systems run concurrently on the same physical server, has become a broadly accepted method to meet these requirements. By converting under-utilized physical servers into virtual machines that run on a single physical server, organizations can reduce space, power and hardware costs in the data center. Because virtual machines are generally much faster to recover in a disaster than physical computers are, virtualization also increases server uptime and reliability.

To help customers adopt virtualization easily, Microsoft has developed a next-generation server virtualization solution as a feature of Microsoft® Windows Server® 2008 R2. HyperVTM is a virtualization platform that out of the box provides reliable and scalable platform capabilities along with a single set of integrated management tools to manage both physical and virtual resources.

Windows Server 2008 R2 adds powerful enhancements to Hyper-V including increased availability, improved management, and simplified deployments. The new version of Hyper-V also includes an exciting feature called Live Migration – the ability to move virtual servers across physical hosts in the datacenter with no perceived downtime for users, so IT can restructure the datacenter as business needs demand without stopping important work streams.

Live Migration provides the highest uptime for virtual machines and enables a dynamic IT infrastructure. The feature facilitates hardware maintenance and upgrades, manual failover, and the consolidation of workloads on fewer servers. With this level of automation in the data center, businesses save on IT costs related to labor, power, cooling and maintenance.

This whitepaper details Live Migration architecture, scenarios, deployment and management. It also highlights other valuable new features available in Windows Server 2008 R2 Hyper-V that help businesses maximize resources and reduce costs. These features include Dynamic VM Storage, Enhanced Processor Support, Enhanced Networking Support and Cluster Shared Volumes (CSV).

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Overview of Windows Server 2008 R2 Hyper-V™ Features

Windows Server® 2008 R2 Hyper-V™ builds on the architecture and feature set of Windows Server® 2008 Hyper-V™ by adding multiple new features that significantly enhance product flexibility. The adoption of virtualization in the enterprise has led to increased flexibility in deployment and life cycle management of applications. IT professionals have deployed and used virtualization to consolidate workloads reducing server sprawl. Additionally they can deploy virtualization with clustering technologies to provide a robust IT infrastructure with high availability and disaster recovery. Even so, customers are looking for higher flexibility. Windows Server® 2008 R2 Hyper-V™ provides greater flexibility with live migration. Live migration is integrated with Windows Server® 2008 R2 Hyper-V™ and Microsoft® Hyper-V™ Server 2008 R2. With Hyper-V™ live migration, you can move running VMs from one Hyper-V™ physical host to another, without any disruption or perceived loss of service. IT professionals are increasingly looking to use live migration to create a dynamic and flexible IT environment which can respond to emerging business needs. Live migration provides the core technology required for dynamic load balancing, virtual machine (VM) placement, high availability for virtualized workloads during physical computer maintenance, and reduced datacenter power consumption.

Windows Server® 2008 R2 Hyper-V™ adds valuable new features to those provided by the first version of Hyper-V™. For example, by using live migration in Windows Server® 2008 R2 Hyper-V™, running VMs can be migrated from one physical computer to another. Storage can be added or removed from a VM while it is running. In addition, Windows Server® 2008 R2 Hyper-V™ takes better advantage of physical computer hardware with greater processor support and deeper support for physical computer hardware. This paper provides an overview of the new features in Windows Server® 2008 R2 Hyper-V™ and detailed information on live migration.

Dynamic VM storage

Windows Server® 2008 R2 Hyper-V™ supports hot plug-in and hot removal of storage. By supporting the addition or removal of Virtual Hard Drive (VHD) files and pass-through disks while a VM is running, Windows Server® 2008 R2 Hyper-V™ makes it possible to quickly reconfigure VMs to meet changing requirements. This feature allows the addition and removal of both VHD files and pass-through disks to existing SCSI controllers of VMs.

Note: Hot add and removal of storage requires the Hyper-V™ Integration Services supplied with Windows Server® 2008 R2 to be installed in the guest operating system.

Enhanced Processor Support

Windows Server® 2008 R2 Hyper-V™ supports up to 32 logical processor cores. The increased processor support makes it possible to run even more demanding workloads on a single physical computer, or consolidate more workloads to a single physical computer.

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Windows Server® 2008 R2 Hyper-V™ also supports Second-Level Address Translation (SLAT) and CPU Core Parking. SLAT uses special CPU functionality available in Intel processors that support Extended Page tables and AMD processors that support Rapid Virtualization Indexing to carry out some VM memory management functions that reduce the overhead of translating guest physical address to real physical addresses. This significantly reduces Hypervisor CPU time and saves memory for each VM, allowing the physical computer to do more work while utilizing fewer system resources. CPU Core Parking enables power savings by scheduling VM execution on only some of a server’s CPU cores and placing the rest in a sleep state.

Enhanced Networking Support

In Windows Server 2008 R2 there are three new networking features that improve the performance of networking in the virtualization environment. Support for Jumbo frames, previously available in nonvirtual environments, has been extended to be available in VMs. This feature enables virtual machines to use Jumbo Frames up to 9014 bytes in size if the underlying physical network supports it. Supporting Jumbo frames reduces the network stack overhead incurred per byte and increases throughput. In addition, there is also a significant reduction of CPU utilization due to the fewer number of calls from the network stack to the network driver.

TCP Chimney, which allows the offloading of TCP/IP processing to the network hardware, has also been extended to work in the virtual world. TCP Chimney improves VM performance by allowing the VM to offload network processing to hardware, especially with networks over 1 Gigabit. This feature is especially beneficial for roles involving large amounts of data transfer such as the file server role.

The Virtual Machine Queue (VMQ) feature allows physical computer Network Interface Cards (NICs) to use DMA to place the contents of packets directly into VM memory, increasing I/O performance.

Cluster Shared Volumes (CSV)

With Windows Server® 2008 R2, Hyper-V™ is able to use CSV storage to simplify and enhance shared storage usage. CSV enables multiple Windows Servers to access SAN storage with a single consistent namespace for all volumes on all hosts. Multiple hosts can access the same Logical Unit Number (LUN) on SAN storage. CSV enables faster live migrations and easier storage management for Hyper-V™ when used in a cluster configuration. Cluster Shared Volumes is available as part of the Windows Failover Clustering feature of Windows Server® 2008 R2.

Live Migration

One of the most highly anticipated new features in Windows Server® 2008 R2 Hyper-V™ is live migration. The remainder of this document describes the live migration feature of Windows Server® 2008 R2 Hyper-V™ in detail, including information on how live migration moves running VMs , describes several scenarios where live migration is particularly useful, and the requirements for implementing live migration.

Live Migration Overview

As stated earlier, live migration is integrated with Windows Server 2008® R2 Hyper-V™ and Microsoft® Hyper-V™ Server 2008 R2. With Hyper-V™ live migration, you can move running VMs from one HyperV™ physical host to another without any disruption of service or perceived downtime.

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Since Hyper-V™ live migration can move running virtual machines without downtime, it will facilitate greater flexibility and value:

Provides better agility: Datacenters with multiple Hyper-V™ physical hosts will be able to move

running VMs to the best physical computer for performance, scaling, or optimal consolidation without impacting users.

Reduces costs and increase productivity: Datacenters with multiple Hyper-V™ physical hosts

will be able to service those systems in a more controlled fashion, scheduling maintenance during regular business hours. Live migration makes it possible to keep VMs online, even during maintenance, increasing productivity for both users and server administrators. Datacenters will be also able to reduce power consumption by dynamically increasing consolidation ratios and powering off un-used physical hosts during times of lower demand.

Live Migration Compared to Quick Migration

Quick Migration is a feature of both Windows Server® 2008 Hyper-V™ and Windows Server® 2008 R2 Hyper-V™. Live migration and Quick Migration both move running VMs from one Hyper-V™ physical computer to another, the primary difference is that Quick Migration saves, moves and restores a VM which results in some downtime. The live migration process uses a different mechanism for moving the running VM to the new physical computer. This process will be explained in greater detail in the Live Migration Architecture section of this document. Below is a summary of the live migration process:

1. All VM memory pages are transferred from the source Hyper-V™ physical host to the destination

Hyper-V™ physical host. While this is occurring, any VM modifications to its memory pages are tracked.

2. ™Pages that were modified while step 1 was occurring are transferred to the destination

physical computer.

3. The storage handle for the VM’s VHD files are moved to the destination physical computer.

4. The destination VM is brought online on the destination Hyper-V™ server.

Live migration produces significantly less downtime for the VM being migrated. This makes live migrations the preferred migration type when users must have uninterrupted access to the migrating VM. Because a live migration will complete in less time than the TCP timeout for the migrating VM, users will not experience any outage for the migrating VM during steps 3 and 4 of the migration.

Note: Windows Server® 2008 Hyper-V™ supports Quick Migration. Windows Server® 2008 R2 Hyper-V™ supports both Quick Migration and live migration.

Live Migration Architecture

Hyper-V™ live migration is designed to move running VMs with no impact on VM availability to users. By pre-copying the memory of the migrating VM to the destination physical host, live migration minimizes the amount of transfer time of the VM A live migration is deterministic, meaning that the administrator, or script, that initiates the live migration can control which computer is the destination for the live migration. The guest operating system in the migrating VM is unaware that the migration is happening, so no special configuration for the guest operating system is needed.

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