[wplug] Virtualization On Boot Flash

[Bryan J. Smith]

Michael Semcheski <mhsemcheski at gmail.com> wrote:
> So how does this sound?  Your machine boots up, looks at the first
> boot drive (which happens to be flash media), which contains a
> stripped down kernel with Xen.  This kernel boots, loads up the
> network and an NFS mount.  Then, it boots the "Mike's Desktop"
> image off of a server.

The biggest, instant and widespread usage I saw of VMWare was just
after EMC bought them.  Overnight virtually anyone and everyone with
EMC SANs started converting to Linux-based ESX Server.  Why?  Because
they were sick and tired of the support issues of running Windows
Server directly on hardware.  I did a bit of consultant doing that
back then.

Whether that is going to take off on the desktop or not may be the
classic Thin Client v. PC debate all over again.  But it certainly
makes it easier to do the former now, on a stock PC.  I think that's
the advantage.  It's still a PITA that Windows doesn't really like to
work in a "read-only" boot (anyone who has built Embedded NT/XP knows
this ;), so it could be a limit for Windows desktops.  Of course that
always translates into more corporate Linux desktop sales.  ;)

> Optionally, it also loads up a Windows desktop if I want one, or
> maybe I want three Linux desktops.  You're only constrained by RAM,
> really.

Well, despite the partitioning instructions in the processors, there
is still some overhead involved.  So it's more than just memory.  ;)

> I think that would be pretty cool.  For one thing, VM's generally
> boot faster than actual PC's.

Er, yes and no.  That depends on your classification and what's
actually going on.  In reality the advantages of VM's have little to
do with boot-up speed, and more to do with "recovery speed" --
especially from snapshots and other images.

I.e., going back to 2004, anyone with EMC SANs wanted Windows off the
bare hardware because they were tired of the "recovery speed" (lack
thereof) when Windows Servers self-toasted.

> Another thing, it adds a layer of
> abstraction between the PC hardware and the OS.  Applications that
> have mutually exclusive dependencies could each get their own
> instance of a VM.

That's one of the classic arguments, yes.

> I think its potentially pretty cool.  I think it would probably be
> feasible with an Intel-VT or AMD-V processor and a USB stick now.
> Thoughts and opinions?

It was feasible before the instructions too, and that's why companies
did it.  But yes, with multi-core desktops, it's very feasible now.

Also understand the virtualization aspect also addresses the
forthcoming "memory limit" of x86-64 as compatible with the i486 TLB.
 "Long mode" can only support up to 48-bit = 256TiB.  Physically, the
current AMD EV6/HyperTransport and Intel IA-32e only support
40-bit/1TiB.


-- 
Bryan J. Smith   Professional, Technical Annoyance
b.j.smith at ieee.org    http://thebs413.blogspot.com
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