[Info-vax] VSI Rolling Roadmap, June 2016

[clairgrant71 at gmail.com]

On Saturday, June 11, 2016 at 4:57:34 AM UTC-4, Paul Sture wrote:

> 
> Has anyone come across a comparison of kvm and xen?  I've looked several
> times over the last 5 years or so but came up with a blank each time.
> 

I can't give you a side-by-side comparison but I have worked with both during the last year and they are very different. Kvm is what I would call a classic hypervisor, a SW product that runs on top of an OS. Some might call it middleware or maybe a sophisticated application. It creates and manages virtual machines and uses the features of the underlying OS to facilitate most operations. Xen is close to being a pure, bare-metal hypervisor but not quite. Xen itself consists of memory management, scheduler, and CPU management but it has no device drivers. Domain 0, a special virtual machine, runs a complete OS, in my case CentOS but it can be others. Xen creates an in-memory "path" between each regular vm and Dom0's I/O system for device access. That's the big architectural difference between kvm and xen.

Most hypervisors default to booting BIOS in the virtual machines. VMS wants UEFI. KVM (and VirtualBox) have a nice option for that and it is also easy to toss in your own boot loader, exactly what we want. Xen isn't as easy since you have to rebuild xen to include UEFI, at least in the version I'm using.

One interesting thing about xen is that there are multiple schedulers available, usually for specific types of workloads.