Re: Virtual Sharing Devices

["rb_ziggy" <rb.lists@xxxxxxxxxxxx>]

--- In ukha_d@xxxxxxx, Nick Austin <nick.w.austin@...> wrote:
>
> On Mon, Oct 12, 2009 at 10:28 PM, rb_ziggy <rb.lists@...> wrote:
> > I was just catching up on a podcast when this company
> > (www.ncomputing.com) was mentioned.
> >
> > Allows multiple users to share one PC by using some
virtualisation software
> > on the pc and a small device per user (either network attached or
direct
> > attached) to connect multiple users (screen, keyboard, mouse) to
the same
> > pc with their own virtual space/machine.
>
> Until the 1970's that's the way almost all computing was done.
> Operating Systems were considered to be one of two types, Single User
> or Multi User.  See:
> http://en.wikipedia.org/wiki/Multi-user

Er, yes thanks.  I'm pretty sure the PC I'm using right now is more
powerful than the Burroughs 'B series' mainframes that I started working on
in 1985.

And yes, the irony of the situation had not escaped me that we are
effectively reinventing the multi-user 'mainframe' concept based on a
single PC as the central hub with dumb terminals! (oh yes, we call it a
'server' now...) Basically because the PC is effectively so powerful.


>
> This made sense when hardware was hugely expensive and the Central
> Processing Unit had to sit inside it's own air-conditioning room.  The
> ordinary user accessed the CPU via a dumb character-based terminal,
> nowadays called the 'thin client'.

Actually, the centralised concept still makes sense as a multi-use utility
computing platform.  Of course we have with VMs on utility hardware - more
or less - reinvented the central multiprocessor multiplexed mainframe
hosted in the air-conditioned datacentre anyway. Deja Vu...

>
> > And it struck me, could have very handy uses in a HA envt.
>
> Things have moved on.  Everyone wants graphics these days and that
> means that the 'thin client' is just a mini-PC.
>
> You can still do it relatively cheaply using Linux.  Each clients
> starts of in text-mode then runs telnet/ssh over ethernet to log into
> the central processor.  You then run X11 (aka X Windows) to bring up
> the desktop.  These are technologies that haven't changed in years so
> you can apply updates to the central server without breaking the
> clients.

Well, no, not quite... This is where things seem to be different (if I read
the specs right).  First, the end device is not a mini-PC at all.  It's a
comms unit that runs an efficient (ok proprietary) protocol back to the pc
itself.  It's low power, relatively cheap and is basically, totally
dedicated to this sole task.  Second, on the PC, session virtualisation
(again proprietary) runs over the o/s to give each user their own session
and access to shared resources / applications. This is completely
transparent to the user - switch on the screen and log onto Windows.  In a
way, very much like switching on the 3270 terminal - but prettier;-)

Of course, this is indeed almost certainly an optimised form of the X
Windows idea and I wouldn't mind betting that those hardware devices are
running some form of embedded Linux.

But what seemed attractive from the HA perspective (and for schools etc)
was:
- Quite cheap, small, very low power, simple client devices that are plug
and play.  No need for 'kiosk' PCs etc around the place.
- Above, reusable if you upgrade client screens (subject to screen
resolution limits) or the server.
- 'Easy'. That is plug and play - no need to design / acquire / build / set
up each of those end mini-pcs and then maintain / reboot etc.
- One server that runs all the screens around the house plus can run as the
ha server.  Simpler to manage, cheaper to run.
- Greener (well ok, helps reduce my power bill anyway).

What I'm not so sure about under this arrangement is HA peripherals plugged
into the server.  Which user can see these??? I have a bunch of things
plugged into serial, usb and the network on the HA server.  I actually only
need these to be visible to the 'HA server application' user so I think
this may still be ok.  All other users will be 'clients' which just
communicate via the HA server application.

And what may be a real problem is that these devices will run a screen,
keyboard and mouse (PS2 type).  I need to run touchscreens and I'm not sure
how they will cope with the usb/serial touchscreen interfaces and
potentially buggy driver software on the server. (They do have a USB plug
on the device but it's intended for a memory stick type application rather
than general - I guess that would be 'universal'- usb application.)

Of course, as an aside, the next step would be to chuck away my server and
put my HA software on some kind of utility server platform that I could
rent somewhere out on the net.  I just need a nice big (100Mb?) internet
connection.  Nah, must get my head out of the 'clouds'...





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