[Info-vax] OpenVMS on x86 and Virtual Machines -- An Observation

[gezelter at rlgsc.com]

On Wednesday, January 30, 2019 at 1:57:57 PM UTC-5, Phillip Helbig (undress to reply) wrote:
> In article <8f9a7157-ac0c-4471-a725-ce52ffa4a86c at googlegroups.com>,
> gezelter at rlgsc.com writes: 
> 
> > Traditionally, OpenVMS has been run on dedicated hardware. 
> 
> > With the advent of OpenVMS on x86, there is an increasing discussion of 
> > running OpenVMS x86 on various virtual machine hypervisors 
> 
> Since VMS will soon run natively on x86, what is the motivation to run 
> it on some sort of emulator?

Phillip,

Not an emulator. Under a hypervisor.

Many organizations have gone to an infrastructure based upon blades and SANs. While it is possible to provision physical hardware in such configurations, the most prevalent allocation strategy is to provision virtual machine instances, which are mapped to full/fractional shares of physical hardware. In such a configuration, one is often not able to run on bare hardware.

The program that manages the real hardware in such a configuration is referred to as a hypervisor. Strictly speaking, a hypervisor is a virtual machine manager, providing a protection between virtual machines, but not changing the underlying instruction set. An x86 virtual machine still runs the x86 instruction set.

An emulator provides for a different instruction set (e.g., VAX, Alpha) than the underlying hardware. This generally involves some form of translation on the fly.

- Bob Gezelter, http://www.rlgsc.com