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Virtual Machine Settings


Now that you’ve created a new VM using the wizard, let’s look at the VM’s setting. To do so, select the newly created VM in the Hyper-V Manager, and click Settings. The Settings dialog is broken into two sections: Hardware and Management. The hardware options control the hardware that’s available to the VM, and the management options control the VM’s administrative tasks. We’ll look at all the options available.

Just like a physical system, a VM consists of a variety of (virtual) hardware devices. In the settings for a VM, you can modify that hardware—including adding processors, network adapters, and hard disks.

Add Hardware
You can modify the configuration of the VM by adding hardware, such as a small computer system interface (SCSI) controller or additional network interface, to the VM. The VM must be powered off to add hardware to the VM. After you add the virtual hardware to the VM and power on the VM, the OS will recognize the new hardware.

Hyper-V doesn’t allow direct access to the Basic Input/Output System (BIOS), so the only BIOS settings you can modify are exposed here:

• Num Lock. Selecting this check box triggers Num Lock in the VM to be active on boot.

• Startup Order. This option controls the order in which devices will be queried for boot. The top-most option will be tried first, and if it fails, then the next option will be tried. By default, the boot order is CD, IDE, legacy network adapter, and then floppy.

You can adjust the amount of memory allocated to the VM. This can range from 8MB to the maximum amount of RAM in the system. There are some caveats:

• Once the VM is powered on, the memory is allocated to the VM and can’t be reclaimed until the VM is saved or turned off.

• Memory allocated to a VM can’t be shared. If multiple VMs are running the same OS,
Hyper-V doesn’t provide the capability to share common pages of memory between the VMs.
• Hyper-V doesn’t provide support for allocating more memory than is available on the host. This limits the amount of memory available to allocate to VMs to about 1GB less than the maximum amount of RAM in the host.

The Processor Settings dialog has a number of options. Hyper-V supports up to four virtual processors in the VM. Those virtual processors are scheduled as threads on the physical processors. A VM can’t have more virtual processors allocated than are present in the host. That means that in order to create a four-core VM, the host system must have at least four cores.

The upper limit of total virtual processors you can allocate on a host is eight times the number of logical processors. A single dual-socket, dual-core server (exposing 4 processors to the host) can support a total of 32 virtual processors. You should keep a very close eye on performance to ensure that the system can handle all the running VMs as well as the host.

Additionally, the Processor Settings dialog is where you set the resource-control options for the VM. This dialog includes the following options:

• Virtual Machine Reserve. This reserves a set amount of processor power for the VM. You can think of this reserve as a guaranteed amount of processor resources.

• Virtual Machine Limit. This is a hard cap on the amount of processor power that the VM can take from the host.

• Relative Weight. The relative weight is another method of assigning a value of importance between multiple VMs. You can set this option to any value from 1 to 10,000. If two VMs have the same VM reserves and limits, the VM with a higher relative weight will receive more processing power.

• Processor Functionality. The last check box in the processor settings controls the processor functionality. By selecting this option, you’ll let older OSs, such as Windows NT or earlier, work with Hyper-V.

It’s important to know the differences between a logical processor and a virtual processor. Logical processors are the foundation of today’s multicore processors. A system with a single core and without Hyper-Threading has a single logical processor. Adding additional cores increases the logical processor count. For example, a system with two physical processors, each processor having two cores, has a total logical-processor count of four. A virtual processor is seen on the host as a single thread of execution, which can then be scheduled on any of the logical processors in the system.

IDE Controller
Hyper-V includes a dual-channel IDE controller much like many standard hardware PCs. By default, a single VHD is connected to the primary IDE controller in the primary connection, with a CD/DVD drive connected to the primary connection of the secondary controller.

The VM can boot only from a VHD connected to the IDE controller. Although this does seem strange and counterintuitive for performance reasons, this arrangement is necessary because of the architecture of Hyper-V. The synthetic devices in Hyper-V aren’t seen in the OS without the integration components being installed.

By clicking the IDE controller, you can add a new hard disk or DVD drive to the specific IDE controller. (DVD drives can be connected only to the IDE controllers.) If you select a hard disk, you have a number of options to choose from. At the top, you can select the specific location where the VHD file will be connected the top. If no SCSI controllers have been added to the VM, then you can add the new VHD to one of the pre-existing IDE controllers only. However, if you added a SCSI controller to the VM’s configuration, then the SCSI controller and all available locations will be listed as well.

After you’ve assigned the new VHD to a specific location, you can set up the specifics of the disk. A number of Hard Drive settings are available, including creating a new VHD, using an existing disk, or editing or inspecting an existing disk. The New, Edit, and Inspect buttons all map back to the New Virtual Hard Disk Wizard. This wizard provides a one-stop interface for all tasks having to do with VHD files.

The bottom option, Physical Hard Disk, lets you directly connect a physical logical unit number (LUN) to a VM. This allows the VM to use directly storage volumes that are connected to controllers on the host—including fibre channel, Internet SCSI (iSCSI), or direct-attached SCSI storage. The use of physical hard disks lets you treat your VMs the same way as physical machines, and you get an increase in performance compared to the default dynamically expanding VHD. In order to connect a physical hard disk to a VM, you must mark the physical disk Offline on the host. You can do this by opening the Disk Management MMC snap-in, selecting the disk, and then right-clicking it and selecting Offline. Take care that you don’t bring the same volume online while the VM has it mounted, or you may lose data.

Network Adap ter
You have several items to choose in the Network Adapter Settings window, and you can change the same settings regardless of the type of network adapter—normal or legacy.

• Network. Each network adapter defined in the Settings dialog can be connected to a single virtual network.

• MAC Address. The Media Access Control (MAC) address of a network adapter is what makes each network adapter unique.

Hyper-V gives you the ability to assign a static MAC address to each network adapter in the VM or to use a dynamically generated MAC address. Some applications use the MAC address of a system for a number of purposes. To set a static MAC address, click the Static radio button and enter the value.

Dynamic MAC addresses under Hyper-V always start with 00:15:5D, with the last three octets randomly chosen based on the MAC address of the host’s physical adapter.

• Enable Virtual LAN Identification. If the VM needs to communicate over a specific virtual local area network (VLAN) using the 802.1q protocol, enter the VLAN ID here. Multiple virtual network adapters can be connected to different VLANs.

COM Port
The COM ports in the VM can either be left unconnected (the default selection) or be connected to a named pipe. Named pipes are a special way of communicating between two different systems.

To connect a virtual COM port to a named pipe on the local system, enter the name of the pipe in the Pipe Name text box. There’s no need to format it in the traditional \\.\pipe\pipe syntax; the dialog box takes care of that. To connect to a remote pipe on another system, select the Remote Computer check box and enter the name of the computer.

A VM has a single virtual floppy disk drive. The virtual floppy drive has no access to the physical floppy disk drive—rather, it uses virtual floppy disks (VFD files). You can create VFD files by using the Virtual Disk Wizard (New -> Floppy Disk).

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


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