Virtualization terms

Update: A newer version of this post (find it here) was recently created. 2

Okay, before I forget, I’m writing it all down.

We have to test against all this stuff, and it’s becoming more and more convenient to use virtualization as a way to share lab resources, so I figured I’d go make sense of all the terminology that’s flying around.  I understood 80% of it, but I could never understand all of it at once.  A lot of this was extracted from Wikipedia.

Here are the things that affect my life: Xen, VirtualBox, VMWare, LDOMs, Zones, Containers.

Hypervisor : Software that emulates a hardware platform, so that Operating Systems can run on top of it, as if they had hardware to run on.

OS Virtualization: When you have one OS (one kernel) running multiple user-spaces. Applications think they are on separate machines.

There are two kinds of Hypervisors, some run directly on hardware (Type 1), and some run as applications (Type 2).

With those terms defined, here is a description of the technologies, features, products that I listed at the top:

  • Hypervisors:
    • Running on hardware – Type 1 Hypervisor
      • Xen: Hypervisor that runs on hardware, supports x86 (aka Sun xVM)
      • LDOMs: Hypervisor that runs on hardware, supports SPARC
    • Running as an application – Type 2 Hypervisor
      • VirtualBox: Hypervisor that runs as an application, supports x86
      • VMWare: Hypervisor that runs as an application, supports x86
  • OS Virtualization
    • Solaris Containers/Zones

The terms “zone” and “container” seem to interchangeable. I have not found a source that is both clear and authoritative that can tell me the difference.

Zones are capable of running different versions of Solaris inside one Global OS instance.

There are lots of things I glossed over here, but my goal was keep it short and sweet.

Trivia:

  • You can run a specific old version of Linux inside a Solaris zone.
  • The VMWare company probably supports products on other chips than x86
  • There are lots of differences between the features of Xen and LDOMs that I didn’t discuss

2 Responses to “Virtualization terms”

  1. Jeff Berkowitz says:

    Concise and useful. Thanks. Another term that sometimes crops up is the “type 1” versus “type 2” hypervisor. As I make it out, “type 1” is your “hypervisor that runs on the hardware”, and “type 2” is your “hypervisor that runs as an application”. Correct me if wrong.

  2. Chris Quenelle says:

    Thanks for pointing this out, Jeff! I think the Type 1 and Type 2 terminology is widely used, and it’s important to know if you want to understand what people are talking about. I updated the blog post to include those terms.