Virtualization in Windows Server 2008 R2 provides both client-server virtualization and presentation virtualization functionality. In this two-part look at Microsoft virtualization, we will cover client-server virtualization (OS virtualization) using Hyper-V and presentation virtualization by using Remote Desktop Services' RemoteApp.
Virtualization has arrived in enterprise IT thanks to the benefits it confers in decreased power usage and lowered hardware acquisitions; two factors that reduce total cost of ownership (TCO), which almost always makes management happy.
What can be virtualized? With today's technology, everything from server or client operating systems to software applications can be virtualized. End users can also use thin clients to run virtual machines, running the operating system image off a server without a performance hit.
Hyper-V is Microsoft's solution for a server virtualization. Hyper-V is a hypervisor-based virtualization on x64 system. Unlike previous, software-based virtualization products by Microsoft such as Virtual PC or Virtual Server 2005, Hyper-V relies on a hardware-based hypervisor, allowing virtual machines to utilize the hardware without going through the host operating system, enabling greater performance and more efficiency for the virtual machine.
As shown in Figure 1, below, the root partition contains the host operating system and other child partitions which in turn contain the guest operating systems, which need to go through the same VMBus before they can talk to the hypervisor and physical hardware. This is an improvement over the previous virtualization software, where the child/guest operating systems needed to talk to the host operating system before they could utilize hardware resources. Thanks to the improved arrangement, all virtual machines will have an equal share of the hardware resources, and will prevent "deadlock" from happening.
Complaints About Hyper-V 1.0
Microsoft's competitor in the virtualization industry, VMWare, is many steps ahead of Microsoft. VMWare's early lead attracted a lot of customers to its virtualization ecosystem. Compared to VMWare, the major setbacks for Hyper-V lie in its inability to dynamically provision virtual machines and disaster recovery. Another big disadvantage is its lack of support for guest operating systems. VMWare ESX supports practically every operating system ever built on almost every type of hardware, but Microsoft's Hyper-V supports only select Microsoft server and client operating systems.
Another major strike against Hyper-V 1.0 was its inability to do a zero downtime migration, which required moving the VM state and the storage. Such a move could take anywhere from a few minutes to a few hours, depending on the storage size involved. Using VMWare's VMotion, state and storage can be moved over in less than a second.
Introducing Hyper-V From Windows Server 2008 R2
It's commonly believed that the first release of most Microsoft products does not attract major customers, with the company iteratively refining its offerings over subsequent versions. That pattern holds with the release of Hyper-V 2.0, which comes with Windows Server 2008 R2. Among the more important key features:
- Live Migration: Live Migration is a key selling point for Hyper-V 2.0. As long as the virtual machines are stored in a LUN (Logical Unit Number) in a Cluster Shared Volume (CSV), it is possible to do a zero downtime migration of a virtual machine from one physical server to another physical server.
- Cluster Validation Tool: Cluster Validation Tool in Windows Server 2008 R2 has been enhanced to include scanning and examining cluster configuration for virtual machines. In the past it has been a challenge to properly configure clusters, but it has now been simplified in Windows Server 2008 and above.
- Hot plug-in and hot removal: Have you ever needed to add storage capacity without any downtime? If the system drive or certain application is running out of disk space, you can now mount a new VHD drive to the virtual machine and span the newly extra disk without any downtime.
- Support for more logical processors: Hyper-V 2.0 supports up to 64 logical processors, up from 16 in Hyper-V 1.0. This means that IT administrators can set up more virtual machines in a single physical server, potentially saving more storage space and decreasing power consumption.
- TCP Offload for VM: TCP Offload allows the CPU to pass the processing load to the NIC, relieving some load on the CPU. Hyper-V 2.0 extends support for TCP Offload for VM, so it is now possible for the virtual machines to pass the processing workload from the virtual CPU to the physical NIC.
While this article has covered on server virtualization by using Microsoft's virtualization technology – Hyper-V. Our next article will cover RemoteApps for Windows Server 2008 R2 and how it can help us virtualize our software applications.