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Type 1 and Type 2 Client Hypervisors

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This post is based on insight gained from two of Brian Madden’s posts: A deeper look at VMware’s upcoming bare-metal client hypervisor and Bare-metal client hypervisors are coming — for real this time

Wikipedia distinguishes between two distinct types of hypervisors

Type 1 Hypervisor

Type 1 (or native, bare-metal) hypervisors are software systems that run directly on the host’s hardware to control the hardware and to monitor guest operating-systems. A guest operating system thus runs on another level above the hypervisor. Some examples are VMware ESX, Xen, Microsoft Hyper-V, etc.

Type 1 hypervisors are appropriate when you want to provide the only OS that is used on a client. When a user turns a machine on, he only sees a single OS that looks and feels local.

Type 2 Hypervisor

Type 2 (or hosted) hypervisors are software applications running within a conventional operating-system environment. Considering the hypervisor layer as a distinct software layer, guest operating systems thus run at the third level above the hardware. Some examples are VMware Workstation, VMware FusionMED-V, Windows Virtual PC, VirtualBox, Parallels, MokaFive, etc.

Type 2 hypervisors are appropriate when you want a user to have access to their own local desktop OS in addition to the centrally-managed corporate VDI OS. This could be for an employee-owned PCscenario, or it could be a situation where you have contractors, etc., who need access to their personal apps and data in addition to the company’s apps and data.

Client Hypervisors

Over the past 5 years, Type 1 hypervisors are dominantly used in the server market, whereas, Type 2 hypervisors are being used on clients, i.e., desktops and laptops. Recently, the need for a Type 1 hypervisor that runs locally on a client device, called the client hypervisor, has emerged for supporting the Virtual Desktop Infrastructure VDI).

Benefits

VDI’s promise lies in realizing a significant cost reduction for managing desktops. A client hypervisor is useful because it combines the centralized management of VDI with the performance and flexibility of local computing. It offers several advantages:

  • It provides a Hardware Abstraction Layer so that the same virtual disk image can be used on a variety of different devices.
  • The devices do not need a “base OS” when the client hypervisor is present. The maintenance overhead of patching a “base OS” frequently on each of the devices is greatly reduced.
  • Once a virtual disk image has been provisioned, it runs and the display is driven locally. This frees up the client from the need to support remote display protocols.
  • It decouples the management of the device from the management of Windows and the user; administrators can spend their time focusing on user needs instead of device maintenance.

Type 1 Server and Client Hypervisors

Server hypervisors are designed to make VMs portable and increasing the utilization of physical hardware. Client hypervisors are intended to increase the manageability of the client device and improve security by separating work and personal VMs.

The bottom line is that even though they’re both called “Type 1” or “bare-metal hypervisors,” there are some philosophical differences in how each came to be. (This could help explain why it has taken over five years to extend the Type 1 hypervisor concept from the server to the desktop.)

Dimension Type 1 Server Hypervisor Type 1 Client Hypervisor
Design Goal Host multiple VMs and make each VM seem like a “real” server on the network. The user shouldn’t even know that there is a hypervisor or they are using a VM.
Virtualization Goal I/O: Disk and Networking Native device support that affects user experience, e.g.,
a) GPU and graphics capabilities
b) USB ports and devices
c) Laptop battery and power state
d) Suspend/Hibernate states
Tuning Maximum simultaneous network, processor and disk I/O utilization Graphics, multimedia and wireless connectivity
Hardware Support Narrow set of different preapproved hardware models Should (ideally) run on just about anything
Intrusiveness Controls most if not all of the hardware platform and devices and provide a near complete emulated and/or para-virtualized device model to the virtual machines running on top a) Should support full device pass-through to a guest VM.
b) Should also support dynamic assignment and “switching” of devices between different guests


Type 1 Client Hypervisor Vendors
In the Type 1 client hypervisor space, there are Neocleus NeoSphere and Virtual Computer NXTop. There are product announcements from both VMware and Citrix, however, there is no shipping product to date. There is also the Xen Client Initiative – an effort to port the open source Xen hypervisor to the client.

Editorial Opinion
Today, hypervisors are a commodity. While they are indeed foundational technology, they are “out of sight is out of mind”, i.e., most users do not perceive their presence and hence ascribe no/low value for this technology. Hypervisor developers will be hard pressed to build a lasting public company solely based on selling hypervisors.

2 Responses

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  1. Please note:

    RingCube does not include, ship, use, or require any type 1 or type 2 client hypervisor. In fact, vDesk can run on any PC, any VDI, or any client hypervisor that has a Windows desktop OS.

    RingCube developed it’s own “Workspace Virtualization Engine (WVE)” that has over 24 patent submissions. Our virtualization engine does not carry a guest operating system. It runs on top of XP, Vista, or Windows 7. Our 64-bit version has been co-developed with Intel Corp.

    And we are very confident it’s the FASTEST desktop virtualization solution in our industry. FASTER than any type 1 or type 2 client hypervisor.

    We are more than happy to conduct a head-to-head benchmark of vDesk WVE vs. type 1 vs. type 2 if folks are interested.

    Again, just wanted to clarify since we were listed under type 2 in your post.

    Doug Dooley

    March 10, 2010 at 10:23 am

    • Doug,

      I appreciate your taking the time to review my post and for providing the clarification. I have removed the reference to RingCube including a Type 2 hypervisor. My statement was based on reading Brian Madden’s post.

      Thanks
      Paul

      paule1s

      March 10, 2010 at 11:09 am


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