[Discuss] SSD

[Jack Coats]

I ran virtual systems on mainframes back when.

There was a neat thing they did then was to basically NOT do virtual
memory on the 'client OS'.  The 'client OS' could figure out it was
being run as a virtual machine, and through special communications
(called Diag back when) would tell the host OS what it needed done.
That way the hostOS actually did all the virtual memory management for
the guest systems.  ... If we turned that off, the overhead on the
guestOS went WAY up.

Normal cpu overhead back then was about 5% to run as in a guestOS
rather than directly in the hostOS.  The first time I remember being
told we were running 'second level', we had been running for a week in
production and no one had noticed any problems. ...

I wonder how todays virtualized systems overhead runs?