Hyper-V is a hypervisor-based
virtualization technology for x64 versions of Windows Server 2008. The
hypervisor is the processor-specific virtualization platform that allows
multiple isolated operating systems to share a single hardware platform. Microsoft
Hyper-V codename Viridian and was formerly known as Windows Server
Virtualization. Hyper-V was first launch
as a beta version with Windows 2008 Server and then finalized version was
released on June 26, 2008. has since
been released in a free stand-alone version.
Hyper-V exists in two variants
1) Stand-alone product called MS
Hyper-V 2008
2) an installable role in Windows 2008
and R2
The standalone version is free and is
part of core installation of Windows 2008.
System
requirement for Hyper-V
Host operating system:
- To install the Hyper-V role, Windows Server 2008 (64-bit only) or 2008 R2 Standard, Enterprise or Datacenter edition is required. Installation on the Web and/or Foundation editions is not possible; neither is it possible on 32-bit (x86-32) versions of Windows Server 2008 nor IA64 editions.
- It can be installed regardless of whether the installation is a full or core installation.
Processor:
- An x86-64 processor
- Hardware-assisted virtualization. This is available in processors that include a virtualization option; specifically, Intel VT or AMD Virtualization (AMD-V, formerly code-named "Pacifica").
- A NX bit-compatible CPU must be available and Hardware Data Execution Prevention (DEP) must be enabled.
- Although this is not an official requirement, Windows Server 2008 R2 and a CPU with Extended Page Table support are recommended for workstations.
Memory
- Minimum 2 GB. (Each virtual OS requires its own memory, and so realistically much more.)
- Windows Server 2008 Standard (x64) Hyper-V full GUI or Core supports up to 31 GB of memory for running VMs, plus 1 GB for the Hyper-V parent OS.
- Maximum total memory per system for Windows Server 2008 R2 hosts: 32 GB (Standard) or 2 TB (Enterprise, Datacenter)
The architecture of Hyper-V is
break-up into 3 rings.
1)
Ring 1
(Hypervisor) : Here the actual hypervisor of Hyper-V is located. This ring does
the actual virutalisation of VMs.
2)
Ring 0
(Kernal Mode) : The kernel mode contains all the necessary components for VM to
runs and interact with other VMs and Host machine. This ring contains device
drivers, VMBus, VSC, etc.
3)
Ring 3
(User mode) : This rings contains the your actual VMs i.e Guest OS and Host OS.
Every OS in Hyper-V is isolated with
each other using a logical terms called as partitions. A partition is a logical
isolation of VMs. Each VM is stored in a separate partition called as child
partition. Same way the Host operating system is also located in a separate
partition called as root/parent partition. The virtualization stacks runs in
parent partition and has direct access to the hardware.
Partition does not have direct access
to physical process. they have a virtual view of the processor and runs in a virtual
memory of each guest partition. The hypervisor handles the processor and memory
request. Moreover child partition also does not have direct access to hardware
resources. The VMBus is a logical inter-partition communication channel which
helps each Host and guest OS to communicate with each other. The parent
partition hosts Virtualization Service Providers (VSPs) which communicate over
the VMBus to handle device access requests from child partitions. Child
partitions host Virtualization Service Consumers (VSCs) which redirect device
requests to VSPs in the parent partition via the VMBus. This entire process is
transparent to the guest operating system.
Acronyms and terms used in the diagram
above are described below:
- APIC – Advanced Programmable Interrupt Controller – A device which allows priority levels to be assigned to its interrupt outputs.
- Child Partition – Partition that hosts a guest operating system - All access to physical memory and devices by a child partition is provided via the Virtual Machine Bus (VMBus) or the hypervisor.
- Hypercall – Interface for communication with the hypervisor - The hypercall interface accommodates access to the optimizations provided by the hypervisor.
- Hypervisor – A layer of software that sits between the hardware and one or more operating systems. Its primary job is to provide isolated execution environments called partitions. The hypervisor controls and arbitrates access to the underlying hardware.
- IC – Integration component – Component that allows child partitions to communication with other partitions and the hypervisor.
- I/O stack – Input/output stack
- MSR – Memory Service Routine
- Root Partition – Manages machine-level functions such as device drivers, power management, and device hot addition/removal. The root (or parent) partition is the only partition that has direct access to physical memory and devices.
- VID – Virtualization Infrastructure Driver – Provides partition management services, virtual processor management services, and memory management services for partitions.
- VMBus – Channel-based communication mechanism used for inter-partition communication and device enumeration on systems with multiple active virtualized partitions. The VMBus is installed with Hyper-V Integration Services.
- VMMS – Virtual Machine Management Service – Responsible for managing the state of all virtual machines in child partitions. Creation of snapshots and adding and removing components are part of VMMS.
- VMWP – Virtual Machine Worker Process – A user mode component of the virtualization stack. The worker process provides virtual machine management services from the Windows Server 2008 instance in the parent partition to the guest operating systems in the child partitions. The Virtual Machine Management Service spawns a separate worker process for each running virtual machine. Its handles start, stop and pause of VMs.
- VSC – Virtualization Service Client – A synthetic device instance that resides in a child partition. VSCs utilize hardware resources that are provided by Virtualization Service Providers (VSPs) in the parent partition. They communicate with the corresponding VSPs in the parent partition over the VMBus to satisfy a child partitions device I/O requests.
- VSP – Virtualization Service Provider – Resides in the root partition and provide synthetic device support to child partitions over the Virtual Machine Bus (VMBus).
