Hyper-V Requirements

Because Hyper-V is included as a role of Windows Server 2008 x64 Edition, it inherits the same hardware requirements. However, a few areas require special attention for Hyper-V.

Hardware Requirements
Some of the requirements for Hyper-V are hard requirements, such as the type of processor, whereas others are best practices to ensure that Hyper-V performs optimally.

Hyper-V requires a 64-bit capable processor with two separate extensions: hardware-assisted virtualization and data-execution prevention. Hardware-assisted virtualization is given a different name by each vendor—Intel calls it Virtualization Technology (VT), and AMD calls it AMD Virtualization (AMD-V). Almost all processors now ship with those features present, but check with your processor manufacturer to make sure. Although the functionality is required in the processor, it’s also required to be enabled in the BIOS. Each system manufacturer has a different way of exposing the functionality, as well as a different name for it. However, most, if not all, manufacturers provide a way to enable or disable it in the BIOS. You can enable it in the BIOS, but some systems don’t enable the feature unless there’s a hard-power cycle—shutting off the system completely, for example. We recommend that the system be completely powered off.

Data-execution prevention (DEP) goes by different names depending on the processor manufacturer—on the Intel platform, it’s called eXecute Disable (XD); and AMD refers to it as No eXecute (NX). DEP helps protect your system against malware and improperly written programs by monitoring memory reads and writes to ensure that memory pages marked as Data aren’t executed. Because you’ll be running multiple VMs on a single system, ensuring stability of the hosting system is crucial.

As we talked about earlier, Hyper-V’s architecture lets you use standard Windows device drivers in conjunction with the VSP/VSC architecture. As such, any of the storage devices listed in the Windows Server Catalog will work with Hyper-V. These include SCSI, SAS, fibre channel, and iSCSI—if there’s a driver for it, Hyper-V can use it. Of course, you’ll want to take some considerations into account when planning the ideal Hyper-V host.

Here are some of the areas where extra attention is necessary:

Multiple spindles and I/O paths. Most disk-intensive workloads, such as database servers, need multiple spindles to achieve high performance. Hyper-V’s storage architecture enables those workloads to be virtualized without the traditional performance penalty. When multiple disk-intensive workloads share the same disk infrastructure, they can quickly slow to a crawl. Having multiple disks (as well as multiple I/O paths) is highly recommended for disk-intensive workloads. Even two workloads sharing a host bus adapter with a single fibre channel can saturate the controller, leading to decreased performance. Having multiple controllers also can provide redundancy for critical workloads.

Disk configurations for optimal performance Hyper-V has a number of different ways to store the VM’s data, each with its own pros and cons:

Pass-through disks:
• Pros: Pass-through disks generally provide the highest performance. The VM writes directly to the disk volume without any intermediate layer, so you can see near-native levels of performance.
• Cons: Maintaining the storage volumes for each VM can be extremely challenging, especially for large enterprise deployments.

virtual hard disks:
• Pros: These are the best choice for production environments using VHD files. Because you allocate all the disk space when you create the VHD file, you don’t see the expansion penalty that occurs with the dynamically expanding VHD.
• Cons: Because all the space for the VHD is allocated at creation, the VHD file can be large.

Dynamic virtual hard disks:
• Pros: A dynamically expanding VHD expands on demand, saving space on the system until it’s needed. Disks can remain small.
• Cons: There is a small performance penalty when a disk is expanded. If large amounts of data are being written, the disk will need to be expanded multiple times.

Snapshots. Snapshots are extremely useful in the test and development environment. However, what can be helpful in one environment can be harmful in another. You shouldn’t use snapshots in a production environment because rolling back to a previous state without taking the proper precautions can mean data loss!

Much like storage, networking with Hyper-V inherits the rich driver support of Windows Server 2008. Many of the caveats for storage apply to networking as well—ensure that multiple NICs are present so a single interface doesn’t become the bottleneck.

The following list identifies areas where you should pay special attention with networking:
• Hyper-V supports Ethernet network adapters, including 10, 100, 1000, and even 10GbE network adapters. Hyper-V can’t use ATM or Token Ring adapters, nor can it use wireless (802.11) adapters to provide network access to the VMs.

• During the Hyper-V role installation you can create a virtual network for each network adapter in your system.

• We recommend that you set aside a single NIC to manage the host. That NIC shouldn’t be used for any VMs (no virtual switch should be associated with it). Alternatively, you can use out-of-band management tools to manage the host. Such tools typically use an onboard management port to provide an interface to the system.

Software Requirements
Hyper-V is a feature of Windows Server 2008 x64 Edition only. There’s no support for Hyper-V in the x86 (aka 32-bit) Edition or the Itanium versions of Windows Server 2008. The x64 Edition is required for a couple of reasons:

Kernel address space The 64-bit version of Windows Server 2008 provides a much larger kernel address space as compared to the 32-bit edition. This directly translates into the support of larger processes, which is crucial for virtualization.

Large amount of host memory Hyper-V supports up to 1 TB of RAM on the host. x86 versions of Windows Server 2008 support only up to 64 GB of RAM on the host, which would severely limit the number of VMs you could run.

We’re frequently asked to explain the differences with Hyper-V between versions of Windows Server 2008. There’s no difference—the features of Hyper-V are the same, regardless of whether you’re running the Standard, Enterprise, or Datacenter product. However, differences in the versions of Windows Server 2008 affect key virtualization scenarios:

Processor sockets. Windows Server 2008 Standard Edition is limited to four sockets, whereas Enterprise Edition supports eight sockets.

Memory. Windows Server 2008 Standard Edition supports up to 32 GB of RAM, and Windows Server 2008 Enterprise Edition supports up to 2 TB of RAM.

Failover clustering. Windows Server 2008 Standard Edition doesn’t include the failoverclustering functionality required for quick migration.

Virtual image use rights. Windows Server 2008 includes the rights to run virtual images of the installed operating system. The number of those virtual images is tied to the edition.

Source of Information : Sybex Windows Server 2008 Hyper-V Insiders Guide to Microsofts Hypervisor

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