When you create a virtual machine, you can customize it by configuring the virtual machine’s settings. You can configure the following logical components:
• Processor. You can configure one to 64 virtual processors to a virtual machine. The number of processors cannot exceed the number of processor cores that you install on the host server.
• Memory. Assign enough memory for the virtual machine and for the role (or roles) that
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Implementing an Advanced Server Infrastructure 4-7
the virtual machine will host. You can assign virtual machines between 8 megabytes (MB) and 1 terabyte of memory. The upper limit cannot exceed the amount of memory installed on the host server.
o You can choose between static and Dynamic Memory. Dynamic Memory allows you to assign a value for a startup amount of memory, including a minimum and maximum, and to choose a percentage for buffering.
• Floppy drive. You can assign only one virtual floppy drive with which you can mount virtual floppy files that are stored in the Virtual Machine Manager library.
• Communications (COM) ports. Allows you to assign up to two virtual COM ports. You configure the virtual COM ports to communicate with the local or a remote physical computer using named pipes.
• Microsoft RemoteFX®3D video adapter. Allows you to use resources on a support physical video adapter in the host. You can assign up to four monitors and resolutions of up to 1920x1200.
• IDE devices. Allows up to four virtual integrated development environment (IDE) devices. You can use these for virtual CD or DVD drives for which you use .iso images that you store in the Virtual Machine Manager library, and then copy to the local host from the library. You also can use these devices for VHDs. All virtual machines that boot from a locally assigned disk must have the boot partition of their supported operating systems on an IDE drive.
• Network adapters. You can use two types of adapters for guest virtual networking. The first, and default, network adapter provides high performance networking, and requires that you install integration services on the virtual machine. You can have up to eight default network adapters in a virtual machine. The alternative is the legacy network adapter, which emulates a specific hardware adapter type and supports Pre-Boot Execution Environment (PXE) to perform network-based installation of an operating system.
• SCSI adapters. You can attach up to four virtual small computer system interface (SCSI) adapters, and each adapter can support up to 64 virtual disks, meaning you can have as many as 256 virtual disks.
You must install integration services to use virtual SCSI adapters.
• Fibre Channel adapter. You can use a Fibre Channel adapter to access Fibre Channel storage directly from the guest operating system.
• Virtual disks. The virtual machine’s purpose determines the type of virtual disk that you choose to use.
A virtual disk is portable. You can move it to another physical disk, another machine, or even to a storage area network (SAN). You also can mount virtual disks within Windows, and then edit their contents. Hyper-V supports the following types of virtual disks:
o Differencing disks. You can use differencing in a parent-child relationship with another disk.
Changes made to the child disk do not write to the parent disk. Differencing makes it easier to conduct fast virtual machine development.
Note: You cannot create differencing disks in VMM, though you can use VMM to manage virtual machines that you create.
o Dynamically expanding disks. These disk types are useful for developing new virtual machines.
o Fixed disks. These provide better performance than dynamically expanding disks. A fixed disk has only the hard drive space that you specify when you create it. If you need more space, then you must extend the disk, attach another virtual hard drive, or use a pass-through disk.
o Automatic virtual hard disk (.avhd). Taking a snapshot of a virtual machine creates an .avhd differencing disk automatically.
When you create a virtual machine, you have several options for creating or attaching a VHD. What you choose will depend on different scenarios, which are described in the following list:
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4-8 Planning and Deploying Virtual Machines
• Create a VHD. This is the default option in the New Virtual Machine Wizard. You can specify the location in which you want to create and install the new VHD and configuration file, or VMM Manager will create and store them in the default location.
• Use an existing virtual hard. You may have created a VHD using the New Virtual Hard Disk Wizard, or you may be using the same hard disk from another virtual machine.
• Attach a VHD later. You create the virtual machine, but will attach a VHD later, perhaps after using the New Virtual Hard Disk Wizard.
• Virtual machine snapshots. When you create a snapshot of a virtual machine, VMM saves it to a subfolder in the folder where you created the virtual machine.
Planning Virtual Machine Configuration
One important goal when developing a virtualization strategy is to simplify and standardize the host computer and virtual machine configuration as much as possible.
Consider the following general guidelines that apply to all the virtual machines:
• Develop a small number of standard virtual machine builds. To streamline the
deployment and management of virtual machines, develop a set of standard virtual machine builds. For example, consider creating a standard low-end server build, a
medium server build, and a high-end server build, then assign a standard central processing unit (CPU) and memory configuration for each role. You also should consider configuring each of the virtual machines with a standard 50-GB system partition, and providing additional disks to store data or install applications. Consider using SCSI controllers for all hard disks other than the disks
containing the boot and system partition. With Windows Server 2012, you can add new VHDs that you connect to a SCSI controller without restarting the server.
• Plan virtual machines for specific server roles. Although you should be able to configure most virtual machines with the same basic disk and operating system configuration, the actual physical
requirements for each virtual machine will vary. For example, some virtual machines will require significantly more RAM or CPU resources than others require. To design the actual physical requirements for a virtual machine, consider the following guidelines:
o Monitor the servers before virtualizing them. Collect performance data on the servers to evaluate how specific applications perform on physical servers. If an application uses a very low
percentage of the hardware resources on a physical server, deploy a virtual server with significantly less capacity to run the same application.
o Configure each virtual server with a hardware configuration that is similar to the hardware required for the application on physical servers. The fact that you are virtualizing a server does not change the hardware resources that the server requires.
• Deploy Windows Server 2012–based virtual machines whenever possible. Use Dynamic Memory, and look for and review any support statements pertaining to virtualization and Dynamic Memory for any application you will host on your virtual machine.
• Consider other options for ensuring physical server utilization. One of the goals of server
virtualization is to ensure that you adequately utilize all servers, whether physical or virtual. You can
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Implementing an Advanced Server Infrastructure 4-9
utilize some server roles fully (such as SQL Server or Exchange Server Mailbox servers), by deploying additional SQL Server instances or moving more mailboxes to the server.
When considering virtualization, review the applications and make use of affinity and anti-affinity. Affinity is the process of grouping certain virtual machines together on single host, whereas anti-affinity is purposely preventing certain virtual machines from deploying to, or residing on, the same cluster nodes.