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Hypervisors - Type 1 / Type 2

SUBMITTED BY JOHN BREDEHOEFT ON WED, 01/04/2012 - 20:48

There is a lot of talk about the Cloud, but what really makes the whole cloud possible is the hypervisor. The hypervisor is what separates the "workload" from physical hardware. This is what allows us to move the workload around, from hardware to hardware. The hypervisor has been around since 1965 with IBM, but only recently has the adoption become exponential. And with the visibility of the Cloud and discussions about Virtual Desktop Initiatives/Infrastructure (VDI) there is now more emphasis on the hypervisor, and the "two types."

There are two kinds of hypervisors that get discussed, type 1 and type 2. I am not going to argue micro-kernel v. macro. I am going to accept the current notions about "type 1" and "type 2" mostly because I think it makes some sense and I can see the distinction. Each type has it's advantages and disadvantages.

Type 1

A "type 1" hypervisor is installed directly on bare-metal hardware, it doesn't require an additional OS, it is the OS, even it it is a light or minimal OS. There are a number of "type 1" hypervisors, let's mention a few:

VMware ESX and ESXi

Citrix Xen Server

Linux KVM

Microsoft Hyper-V. I put Hyper-V last, because if you aren't particular about how you install Windows 2008 you can end up with the Full 2008 OS. This defeats the purpose of having a Type 1 hypervisor.

MokaFive -- this is a desktop hypervisor for Bare-Metal install.

XenClient -- this is also a desktop hypervisor for Bare-Metal installs.

Advantages

There are a number of distinct advantages with "type 1." I've mentioned the first already, installing on Bare-Metal. This is both a feature and a benefit for this type.

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Dis-Advantages

Really, Really large VMs are not supported. At this point I would mean massive. VMware now supports 1000GB (1TB) RAM and 32 CPUs in a VM, so you have to be really big to not be able to run...