A brief architecture overview of Viridian (WSV), VMware ESX, and XEN

Massimo ReFerre from IBM has recently blogged the technical differences between Viridian (WSV), VMware ESX, and XEN.

A few others have blogged this already, but yesterday it ended up in the TechNet Server Virtualization Forums, so I thought it deserved reblogging here.  You can read the full article in his post “A brief architecture overview of VMware ESX, XEN and MS Viridian“, and a snippet is below:

It is my feeling that there has been a bit of confusion lately around how hypervisors are being positioned by the various vendors. I am specifically referring to the three major technologies that seem to be the most relevant strategically going forward:

  • VMware ESX is the VMware flagship hypervisor product: it’s the basis for the Virtual Infrastructure version 3 framework.
  • MS Viridian is the next generation hypervisor that Microsoft is going to use in the Longhorn time frame and that is currently being developed. It’s basically the successor of Microsoft Virtual Server.
  • Xen is an opensource hypervisor that is being integrated by a number of players which include RedHat, Suse, XenSource and Virtual Iron.

….

Back to the point there are really two set of thoughts currently in the industry (I warned you it’s still up in the air). The first thought is that these new hardware assists hardware (especially in future implementations) has diminished the need of paravirtualizing the guest. These hw implementations will be so efficient and optimized that there will be no need to optimize the guest OS as well and even a standard OS (i.e. non paravirtualized) will perform close to native speed. The other thought is that, other than the efficiency and optimization provided by these low level hardware instructions there is room to improve performance by paravirtualizing the Guest OS in areas where Intel-VT and AMD-V would have little effect. This second thought is backed by the fact that given points #1 and #2 above there would be no more supportability issues as Suse, RedHat and Microsoft are going to provide their own fully supported paravirtualized versions of their own OS kernels.

….as I said at the beginning of this third section, this is still pretty much up in the air and these have been speculations on possible future situations that might be proven wrong

The post is a mix of technical and personal commentary, and if time permits is worth a read.