Welcome!

Containers Expo Blog Authors: Liz McMillan, Yeshim Deniz, Elizabeth White, Zakia Bouachraoui, Pat Romanski

Related Topics: Containers Expo Blog

Containers Expo Blog: Article

Hyper-V Terminology: Microsoft's Virtualization Lexicon

Virtual PC, Virtual Server and Windows Virtualization


Virtual PC Guy's WebLog

Well, I just realized that I had dived into talking about how to do things with Hyper-V without first taking the time to orient you on some of the terminology used. So I would now take the time to correct that. Note that many of these terms are not used in the user interface / documentation for Hyper-V. The reason for this is that from an operational 'getting things done' point of view you do not need to know about most of this. However, once you start discussing architecture it becomes necessary to know about this stuff.

However, once you start discussing architecture it becomes necessary to know about this stuff:
  • Hypervisor
    The hypervisor is to Hyper-V what the kernel is to Windows.  The hypervisor is not all of Hyper-V, it is just the lowest level component that is responsible for interaction with core hardware.  The hypervisor is responsible for creating, managing and destroying partitions.  It directly controls access to processor resource and enforces an externally delivered policy on memory and device access.  To give some perspective: the hypervisor is just over 100k in size, the entire Hyper-V role is around 100mb in size and a full installation of Windows Server 2008 with Hyper-V will be multiple gigabytes in size.  Once you have installed the Hyper-V role the hypervisor is loaded as a boot critical device.
  • Virtualization Stack
    The virtualization stack is everything else that makes up Hyper-V.  This is the user interface, management services, virtual machine processes, emulated devices, etc...
  • Partition
    A partition is the basic entity that is managed by the hypervisor.  It is an abstract container that consists of isolated processor and memory resources - with policies on device access.  A partition is a lighter weight concept than a virtual machine - and could be used outside of the context of virtual machines to provide a highly isolated execution environment.
  • Root Partition
    This is the first partition on the computer.  Specifically this is the partition that is responsible for initially starting the hypervisor.  It is also the only partition that has direct access to memory and devices.
  • Parent Partition
    The parent partition is a partition that is capable of calling the hypervisor and requesting that new partitions be created.  In the first release of Hyper-V the parent and root partitions are one and the same - and there can only be one parent partition.
  • Child Partition
    Child partitions are partitions that have been made by the hypervisor in response to a request from the parent partition.  There are a couple of key differences between a child partition and a parent / root partition.  Child partitions are unable to create new partitions.  Child partitions do not have direct access to devices (any attempt to interact with hardware directly is routed to the parent partition).  Child partitions do not have direct access to memory (when a child partition tries to access memory the hypervisor / virtualization stack re-map the request to different memory locations).
  • Virtual Machine
    A virtual machine is a super-set of a child partition.  A virtual machine is a child partition combined with virtualization stack components that provide functionality such as access to emulated devices, and features like being able to save state a virtual machine.  As a virtual machine is essentially a specialized partition, I (and many members on the team) tend to use the terms "partition" and "virtual machine" interchangeably.  But, while a virtual machine will always have a partition associated with it - a partition may not always be a virtual machine.
  • Guest Operating System
    This is the operating system / runtime environment that is present inside a partition.  Historically with Virtual Server / Virtual PC we would talk about a "host operating system" and a "guest operating system" where the host ran on the physical hardware and the guest ran on the host.  With Hyper-V all operating systems on the physical computer are running on top of the hypervisor so the correct equivalent terms are actually "parent guest operating system" and "child guest operating system".  Having said that, most people (apart from architectural die hards) find these terms confusing and instead use "physical operating system" and "guest operating system" to refer to parent and child guest operating systems respectively.
  • Emulated Device
    Emulated devices are the hardware that is presented inside of the virtual machine.  If you have used Virtual Server / Virtual PC you will be quite familiar with this hardware.  It includes things like a Intel 440bx motherboard and an Intel 21140 network adapter.  These devices are handled through emulation that runs in the parent partition.  The advantage of emulated devices is that most operating systems have in-box drivers for them and are able to install and boot using them.  The disadvantage of emulated devices is that because they were not designed with virtualization in mind they do not perform well.
  • Synthetic Device
    Synthetic devices are the new high performance devices that are available with Hyper-V.  Here, rather than emulating an existing hardware device we expose a new hardware device that has been designed for optimal performance in a virtualized environment (I will not go into a performance discussion of synthetic versus emulated devices here - as that is quite a lengthy discussion and can wait for another day).  Generally speaking you will never see reference to a "synthetic" or "emulated" device in our user interface as we have tried to hide this from the user as much as possible. 

    Most of our devices (IDE, video, mouse, etc...) support booting in emulated mode, but then switching across to synthetic mode once appropriate drivers are loaded.  There are some exceptions to this though.  On networking you have to choose to use a "Network Adapter" or a "Legacy Network Adapter".  The former is a synthetic device while the latter is an emulated device.  With storage the "SCSI controller" only exists as a synthetic device.  And finally there are a handful of devices where performance is not really a problem (like COM ports) so we only offer emulated devices for them.
  • Integration Services
    Integration services are user mode processes that run in the child guest operating system to provide some level of "integration" between the parent and child environments.  Some examples include: time synchronization, child guest operating system shutdown messaging and backup support.
  • Integration Services Setup Disk
    This is a CD image that contains the installer for both the integration services and the synthetic device driver.  You use it to get these components on your virtual machine so that you can have the fastest / best user experience.
  • Enlightenment
    Now here there is even some contention inside the virtualization team as to the correct usage of this term.  Some people use this term to refer to changes / intelligence in the guest operating system kernel that allow it to perform faster / with less overhead inside a virtual machine.  While others use it to refer to synthetic devices and integration services as well.  Those of us who use the broader definition will often use the terms "device enlightenment" and "kernel enlightenment" to differentiate between the concepts. 

    I personally fall into the first camp and when I say "enlightenment" I mean "kernel enlightenment".  (There is a whole conversation around enlightenment as a concept, but I am leaving that too for another day).
  • Virtual Machine Snapshot
    As discussed here - a virtual machine snapshot is a point in time image of a virtual machine that includes its disk, memory and device state at the time that the snapshot was taken.  It can be used to return a virtual machine to a specific moment in time - at any time.  Virtual machine snapshots can be taken no matter what child guest operating system is being used and no matter what state the child guest operating system is in.
  • VSS Snapshot
    Unfortunately the term "snapshot" is also used in the Windows world in the context of VSS.  VSS snapshots are complete system backups that should be used for protecting your system against unplanned data loss / hardware failure.
  • Physical Processor
    This is simple.  It is the squarish chip that you put in your computer to make it go.  This is sometimes also referred to as a "package" or a "socket".
  • Logical Processor
    This is a single execution pipeline on the physical processor.  In the "good old days" someone could tell you that they had a two processor system - and you new exactly what they had.  Today if someone told you that they had a two processor system you do not know how many cores each processor has, or if hyperthreading is present.  A two processor computer with hyperthreading would actually have 4 execution pipelines - or 4 logical processors.  A two processor computer with quad-core processors would in turn have 8 logical processors.
  • Processor topology
    This is the concept of how your logical processors correlate to your physical processors.  For instance, a two processor quad core system and a four processor dual core system both have 8 logical processors - but they have different processor topologies.
  • Virtual Processor
    A virtual processor is a single logical processor that is exposed to a partition by the hypervisor.  Virtual processors can be mapped to any of the available logical processors in the physical computer and are scheduled by the hypervisor to allow you to have more virtual processors than you have logical processors.

That seems like a good set to start with.  If there are some that I have forgotten - I will do another terminology post at some time in the future.

More Stories By Ben Armstrong

Ben Armstrong is a Program manager on the core virtualization team at Microsoft. His popular "Virtual PC Guy's Weblog" is at http://blogs.msdn.com/virtual_pc_guy/.

Comments (0)

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


IoT & Smart Cities Stories
Moroccanoil®, the global leader in oil-infused beauty, is thrilled to announce the NEW Moroccanoil Color Depositing Masks, a collection of dual-benefit hair masks that deposit pure pigments while providing the treatment benefits of a deep conditioning mask. The collection consists of seven curated shades for commitment-free, beautifully-colored hair that looks and feels healthy.
The textured-hair category is inarguably the hottest in the haircare space today. This has been driven by the proliferation of founder brands started by curly and coily consumers and savvy consumers who increasingly want products specifically for their texture type. This trend is underscored by the latest insights from NaturallyCurly's 2018 TextureTrends report, released today. According to the 2018 TextureTrends Report, more than 80 percent of women with curly and coily hair say they purcha...
The textured-hair category is inarguably the hottest in the haircare space today. This has been driven by the proliferation of founder brands started by curly and coily consumers and savvy consumers who increasingly want products specifically for their texture type. This trend is underscored by the latest insights from NaturallyCurly's 2018 TextureTrends report, released today. According to the 2018 TextureTrends Report, more than 80 percent of women with curly and coily hair say they purcha...
We all love the many benefits of natural plant oils, used as a deap treatment before shampooing, at home or at the beach, but is there an all-in-one solution for everyday intensive nutrition and modern styling?I am passionate about the benefits of natural extracts with tried-and-tested results, which I have used to develop my own brand (lemon for its acid ph, wheat germ for its fortifying action…). I wanted a product which combined caring and styling effects, and which could be used after shampo...
The platform combines the strengths of Singtel's extensive, intelligent network capabilities with Microsoft's cloud expertise to create a unique solution that sets new standards for IoT applications," said Mr Diomedes Kastanis, Head of IoT at Singtel. "Our solution provides speed, transparency and flexibility, paving the way for a more pervasive use of IoT to accelerate enterprises' digitalisation efforts. AI-powered intelligent connectivity over Microsoft Azure will be the fastest connected pat...
There are many examples of disruption in consumer space – Uber disrupting the cab industry, Airbnb disrupting the hospitality industry and so on; but have you wondered who is disrupting support and operations? AISERA helps make businesses and customers successful by offering consumer-like user experience for support and operations. We have built the world’s first AI-driven IT / HR / Cloud / Customer Support and Operations solution.
Codete accelerates their clients growth through technological expertise and experience. Codite team works with organizations to meet the challenges that digitalization presents. Their clients include digital start-ups as well as established enterprises in the IT industry. To stay competitive in a highly innovative IT industry, strong R&D departments and bold spin-off initiatives is a must. Codete Data Science and Software Architects teams help corporate clients to stay up to date with the mod...
At CloudEXPO Silicon Valley, June 24-26, 2019, Digital Transformation (DX) is a major focus with expanded DevOpsSUMMIT and FinTechEXPO programs within the DXWorldEXPO agenda. Successful transformation requires a laser focus on being data-driven and on using all the tools available that enable transformation if they plan to survive over the long term. A total of 88% of Fortune 500 companies from a generation ago are now out of business. Only 12% still survive. Similar percentages are found throug...
Druva is the global leader in Cloud Data Protection and Management, delivering the industry's first data management-as-a-service solution that aggregates data from endpoints, servers and cloud applications and leverages the public cloud to offer a single pane of glass to enable data protection, governance and intelligence-dramatically increasing the availability and visibility of business critical information, while reducing the risk, cost and complexity of managing and protecting it. Druva's...
BMC has unmatched experience in IT management, supporting 92 of the Forbes Global 100, and earning recognition as an ITSM Gartner Magic Quadrant Leader for five years running. Our solutions offer speed, agility, and efficiency to tackle business challenges in the areas of service management, automation, operations, and the mainframe.