Hyper-VMicrosofts latest Server Virtualization Solution

What is hyper-vVirtualization is one of todays hottest IT technologies, and Windows Server 2008s new native virtualization feature, Hyper-V, is a significant new competitor that has the potential to change the market. VMware ESX Server is the current market favorite. To Know what Hyper-V is , you need to understand how the architectures of the two products compare. In addition, Hyper-V introduces some important new features, and youll want to see how Hyper-V and the older Virtual Server 2005 R2 relate to each other. Finally, to enrich your understanding of Hyper-V Ill show you how to set it up and use it.

Hyper-V Terminology This section summarizes key terminology specific to VM technology

child partition: Any partition (VM) that is created by the root partition.device virtualization: A mechanism that lets a hardware resource be abstracted and shared among multiple consumers.emulated device: A virtualized device that mimics an actual physical hardware device so that guests can use the typical drivers for that hardware device.Enlightenment: An optimization to a guest operating system to make it aware of VM environments and tune its behavior for VMs.Guest: Software that is running in a partition. It can be a full-featured operating system or a small, special-purpose kernel. The hypervisor is guest-agnostic.Hypervisor: A layer of software that sits just above the hardware and below one or more operating systems. Its primary job is to provide isolated execution environments called partitions. Each partition has its own set of hardware resources (CPU, memory, and devices). The hypervisor is responsible for controls and arbitrates access to the underlying hardware.

Logical processor: A CPU that handles one thread of execution (instruction stream). There can be one or more logical processors per core and one or more cores per processor socket. In effect, it is a physical processor.Passthrough disk access: A representation of an entire physical disk as a virtual disk within the guest. The data and commands are passed through to the physical disk (through the root partitions native storage stack) with no intervening processing by the virtual stack.Root partition: A partition that is created first and owns all the resources that the hypervisor does not own including most devices and system memory. It hosts the virtualization stack and creates and manages the child partitions.Synthetic device: A virtualized device with no physical hardware analog so that guests might need a driver (virtualization service client) to that synthetic device. The driver can use VMBus to communicate with the virtualized device software in the root partition.

Virtual machine (VM): A virtual computer that was created by software emulation and has the same characteristics as a real computer.Virtual processor: A virtual abstraction of a processor that is scheduled to run on a logical processor. A VM can have one or more virtual processors.Virtualization service client (VSC): A software module that a guest loads to consume a resource or service. For I/O devices, the virtualization service client can be a device driver that the operating system kernel loads.Virtualization service provider (VSP): A provider, exposed by the virtualization stack, that provides resources or services such as I/O to a child partition.Virtualization stack: A collection of software components in the root partition that work together to support VMs. The virtualization stack works with and sits above the hypervisor. It also provides management capabilities.

Prerequisites for Hyper-V

Unlike Microsofts Virtual Server 2005 R2, which runs on both 32-bit and 64-bit systems, Hyper-V requires an x64-based system that has either Intel-VT or AMD-V support. In addition, the host systems CPU must have data execution protection enabled (the Intel XD bit or the AMD NX bit). Microsoft will provide Hyper-V virtualization technology with the following versions of the Windows Server 2008.Server 2008, Standard 64Bit EditionServer 2008, Enterprise 64Bit EditionServer 2008, Datacenter 64Bit EditionLike the Windows Server 2003 R2, Enterprise and Datacenter Editions, the Server 2008, Enterprise Edition allows up to four virtual Windows instances with no additional licensing costs, and Server 2008 Datacenter Edition allows an unlimited number of virtual Windows instances with no additional licensing costs. You can use Hyper-V with both the full Server 2008 installation, or with Server Core for any of the Server 2008 editions. In addition Microsoft will offer a standalone version called Hyper-V Server.

Windows Server Hyper-V Architecture

Designed to compete with VMwares ESX Server, Hyper-V has been built from scratch based on a new microkernel architecture. The above figure shows an overview of the new Server 2008 Hyper-V architectureUnlike Virtual Servers hosted virtualization model, which requires installing the virtualization software on top of a host OS, Hyper-V is a virtualization layer that runs directly on the system hardware with no intervening host OS. The Hyper-V architecture consists of the bare metal microkernel hypervisor and parent and child partitionsAll Hyper-V implementations have one parent partition. This partition manages the Hyper-V installation. The Windows Server Virtualization console runs from the parent partition. In addition, the parent partition is used to run thread-supported legacy hardware emulation virtual machines (VMs). These older emulation-based VMs are essentially the same as the VMs that run under a hosted virtualization product such as Virtual Server.

Guest VMs run on Hyper-V child partitions. Hyper-Vs child partitions support two types of VM: high performance VMBus-based VMs or hosted emulation VMs. VMBus VMs include Windows Server 2003, Windows Vista, Server 2008, and Xen-enabled Linux. The new VMBus architecture is essentially a high performance in-memory pipeline that connects Virtualization Service Clients (VSCs) in the guests with the hosts Virtual Service Provider (VSP). Hosted emulation VMs support guest OSs that dont support the new VMBus architecture. These OSs include, Windows NT and non-Xen enabled Linux, like SUSE Linux Server Enterprise 10.

StorageHyperV supports synthetic and emulated storage devices in VMs, but the synthetic devices generally can offer significantly better throughput and response times and reduced CPU overhead. The exception is if a filter driver can be loaded and reroutes I/Os to the synthetic storage device. Virtual hard disks (VHDs) can be backed by three types of VHD files or raw disks. The next slide describes the different options

Synthetic SCSI Controller: The synthetic storage controller provides significantly better performance on storage I/Os with reduced CPU overhead than the emulated IDE device. The VM integration services include the enlightened driver for this storage device and are required for the guest operating system to detect it. The operating system disk must be mounted on the IDE device for the operating system to boot correctly, but the VM integration services load a filter driver that reroutes IDE device I/Os to the synthetic storage device.Its recommended to mount the data drives directly to the synthetic SCSI controller because that configuration has reduced CPU overhead. Also mount log files and the operating system paging file directly to the synthetic SCSI controller if their expected I/O rate is high. For highly intensive storage I/O workloads that span multiple data drives, its recommended to attach each VHD to a separate synthetic SCSI controller for better overall performance.

Virtual Hard Disk Types

There are three types of VHD files. Its recommended that production servers use fixed-sized VHD files for better performance and also to make sure that the virtualization server has sufficient disk space for expanding the VHD file at run time. The following are the three VHD types:Dynamically expanding VHD: Space for the VHD is allocated on demand. The blocks in the disk start as zeroed blocks but are not backed by any actual space in the file. Reads from such blocks return a block of zeros. When a block is first written to, the virtualization stack must allocate space within the VHD file for the block and then update the metadata. This increases the number of necessary disk I/Os for the write and causes an increased CPU usage. Reads and writes to existing blocks incur both disk access and CPU overhead when looking up the blocks mapping in the metadata.Fixed-size VHD: Space for the VHD is first allocated when the VHD file is created. This type of VHD is less apt to fragment, which reduces the I/O throughput when a single I/O is split into multiple I/Os. It has the lowest CPU overhead of the three VHD types because reads and writes do not need to look up the mapping of the block.Differencing VHD: The VHD points to a parent VHD file. Any writes to blocks never written to before result in space being allocated in the VHD file, as with a dynamically expanding VHD. Reads are serviced from the VHD file if the block has been written to. Otherwise, they are serviced from the parent VHD file. In both cases, the metadata is read to determine the mapping of the block. Reads and writes to this VHD can consume more CPU and result in more I/Os than a fixed-sized VHD. Snapshots of a VM create a differencing VHD to store the writes to the disks since the snapshot was taken.

Passthrough DisksThe VHD in a VM can be mapped directly to a physical disk or logical unit number (LUN), instead of a VHD file. The benefit is that this configuration bypasses the file system (NTFS) in the root partition, which reduces the CPU usage of storage I/O. The risk is that physical disk or LUNs can be more difficult to move between machines than VHD files.Large data drives can be prime candidates for passthrough disks, especially if they are I/O intensive. VMs that can be migrated between virtualization servers (such as quick migration) must also use drives that reside on a LUN of a shared storage device.

Hyper-V and Virtual Server 2008Hyper-V introduces capabilities that arent available with Virtual Server 2005 R2. Running exclusively on the x64 platform, Hyper-V supports host systems with up to 1TB of RAM, and Hyper-V doesnt limit the number of active VMs; the only limitation comes from the capabilities of the host server hardware. In addition, the Hyper-V VMs are more scalable than Virtual Server VMs. Hyper-V supports both 32-bit and 64-bit guest OSs. Not only can guest VMs take advantage of Hyper-Vs higher performing VMBus architecture, but guest VMs also can use more RAM and CPU than Virtual Server offers. Virtual Server 2005 R2 has no support for virtual SMP and is limited to 3.6GB of RAM per VM. Hyper-V supports up to 4 virtual processors per VM and up to 32GB of RAM per VM. To take full advantage of this support, the host system must have at least 4 cores and more than 32GB of physical RAM.

Hyper-V provides new storage features. Storage Area Network (SAN) support lets you boot VMs and implement guest-to-guest failover clustering, as well as virtual server host failover clustering. Hyper-V also introduces the pass-through VM access storage feature. With Hyper-V, you can access virtual hard disk (VHD) images without mounting the VHD image in a running VM. Hyper-V can also take advantage of Volume Shadow Copy Service (VSS) for live VM backup. On the networking side, Hyper-V includes a new virtual switch with support for Windows Network Load Balancing (NLB) across VMs on separate servers. In addition, Hyper-V allows multiple snapshots of running VMs with the ability to revert back to any of the saved snapshots.

Installing Hyper-VHyper-V is not installed in Server 2008 by default. To install Hyper-V, you use the Server 2008 Server Manager. Click Start, Programs, Administrative Tools, and then select the Server Manager option. In Server Manager, add the virtualization role by clicking Add Roles, which displays the Add Roles Wizard shown in

In the Add Roles Wizard, check the Windows Server virtualization role. Then click Next and step through the wizards screens to learn about and configure Hyper-V. The wizard first explains that you might need to configure your BIOS for virtualization support, and it provides links to Windows Server Virtualization Online Help files. Next, the wizard prompts you for the Local Area Connections that you want to associate with your virtual networks. By default, the wizard creates one virtual network for each physical network adapter thats installed. Next, youre asked to confirm your selections and prompted to restart your system.

AMD-V systems have virtualization support enabled by default. In contrast, if your system uses Intel-VT virtualization, check your systems BIOS configuration during the boot process and make sure that virtualization is enabled. For systems with Intel motherboards, press F2 during the boot process to see the BIOS configuration. You can set the Enable VT option to enable virtualization support in the processor.

After the system reboots, the Resume Configuration Wizard screen appears. Use it to finish installing the Windows Server Virtualization role. The new Windows Server Virtualization role will then be listed under Server Managers installed roles node.After the virtualization role is installed, youre ready to fire-up some new VMs. Unlike Virtual Server 2005 R2, which you manage through a Web-based console, Hyper-V is managed through a Microsoft Management Console (MMC) 3.0-based Windows GUI. You start Hyper-Vs Virtualization Management Console by clicking Start, Administrative Tools, and then selecting Windows Virtualization Management.

Use the Wizard to Create and Migrate VMs Creating VMs is easy using Hyper-Vs New Virtual Machine Wizard. To start the wizard, click New in the Virtualization Management Console Action pane.The first screen prompts you for the VM name and the location where the VM will be created. By default, Hyper-V creates new VMs in the C:\ProgramData Microsoft\Windows\Virtualization directory. To change the default location, you can use Virtualization Settings in the Virtualization Management Console. Next the wizard prompts you for the amount of memory allocated to the VM. The default value is 256MB, but you can allocate from 8MB to 32MB of RAM per VM (limited by your systems physical RAM).

Next, the wizard asks you about networking the VM. You can choose no network or select a virtual network. The wizard created virtual networks when you first added the virtualization role. To create virtual networks, you can also use Virtual Network Switch Management in the Virtualization Management Console. You can configure the virtual network switch to allow internal networking so that VMs can connect with other VMs or to the Windows Server host. You also can create a virtual network that connects to one or more of the hosts physical network adapters for external network connectivity.

The New Virtual Machine Wizard gives you the option of creating a VHD, connecting to an existing VHD, or attaching to a VHD later. By default, VHDs are created in the C:\Users Public\Documents\Virtual Hard Disks directory. To change this default directory, you can use Virtualization Setting in the Virtualization Management Console. Hyper-V uses the same on-disk VHD format as Virtual Server 2005 R2. This common format makes it easy to migrate existing Virtual Server 2005 R2 and Virtual PC VMs to Server 2008 Hyper-V: Select the option to use an existing VHD and then provide the wizard with the path to the VHD file. This attaches the existing VHD to the new Hyper-V VM. If you chose to use a new VHD, then the next screen offers OS installation options. You can install the OS later or install the OS from either the hosts CD/DVD drive or from an ISO image file. The last screen presented by the wizard prompts you to confirm your VM configuration settings. Finishing the wizard creates the new VM automatically. You have the option to start it right away or you can manually start it later.

After a VM is created you have the option to install the new Integration Services on the guest. (Before you install Integration Services we need to uninstall the virtual server additions) Integration Services replaces the older Virtual Machine Additions. Integration Services provides improved mouse support and host time synchronization. You can install Integration Services on the guest OS by starting a Virtual Machine Connection from the Virtualization Management Console. From the Virtual Machine Connection Action menu, choose Insert Integration Services Disk.

Microsoft shipped a beta version of Hyper-V in December 2007. A prerelease version of Hyper-V was shipped with the RTM of Server 2008. Microsoft also released RC0 & RC1 of Hyper-VMicrosoft had stated that the final Hyper-V code will ship within 180 days of the Windows Server 2008 release to manufacturing (RTM). Microsoft released the RTM of Hyper-V on 26th June 2007 for download on Microsoft download centre http://www.microsoft.com/downloads/details.aspx?FamilyID=f3ab3d4b-63c8-4424-a738-baded34d24ed&DisplayLang=enThe Hyper-V RTM was released via Windows Update on 8th July 2007An update to remotely manage the Hyper-V role from windows vista machine on the network is KB952627, the update is available in both 32Bit & 64Bit versions