[Info-vax] VMware

[Bob Gezelter]

On Tuesday, December 10, 2019 at 10:14:12 AM UTC-5, Craig A. Berry wrote:
> On 12/9/19 7:34 PM, Grant Taylor wrote:
> 
> > VMs also offer a redundancy / hardware abstraction layer that hardware 
> > can't match.
> > 
> > It's trivial to (re)start a VM on another host, even when the host it 
> > was running on throws sparks and flames or otherwise turns into a pile 
> > of slag.
> 
> Doesn't being able to do that depend on OS capabilities that quiesce
> everything while the running instance is being moved?  I wouldn't expect
> a lot of the usual VM capabilities for OpenVMS instances on first
> roll-out, but it would still be very nice to have it running on VMWare,
> even if managing it is still mostly done the old-fashioned way for now.

Craig,

Your assertion with regards to the instance being effectively quiesced during migration is correct in concept, but it is incomplete. 

Large, if not the overwhelming majority of memory is not writeable or not actively being written at any given instant. Present write and I/O remain an issue. Block I/O initiation on mass storage and one can quiesce those I/Os. Network I/O will appear as lost packets, recoverable by normal error recovery mechanisms. In effect, the situation is not particularly different than a traditional power failure/recovery interrupt.

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