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Re: [Qemu-devel] Qemu - where will it go?

From: Thomas Steffen
Subject: Re: [Qemu-devel] Qemu - where will it go?
Date: Sat, 14 Jan 2006 18:35:29 +0100

Hi Juergen!

On 1/14/06, Juergen Pfennig <address@hidden> wrote:
> as I found out qemu is quite stable and has acceptable performance. Using it 
> you
> could freeze legacy applications using a legacy OS like win 2003 or win XP. I 
> am
> talking of periods from 5 to 20 years!

Yes, that is a good idea. Having a defined VM is probably the most
stable computing environment you can get. If it is a well used one,
all the better. I have seen research projects that would build a
custom VM in Java (!), and then program a PDF viewer for this VM.
Which is of course mostly useless, compared to all the great things
you can do with Qemu, and without Java.

> But a lot of work would have to be done. The next steps of development would
> probably include:
> - run qemu as a service (on Windows or on Linux using xinetd)
> - make rdp (Win Terminal Server) work when qemu started via
>   xinetd
> - improve disk image format, better snapshot handling
> - make a plugin architecture for the host side device implementation
> - allow 'remote' host side devices (sound, usb, serial ...)
> - define a protocol to use qemu over a network (should multiplex
>   video, sound, usb, serial and so on).

While I agree that all these ideas are nice, I am not sure they are
essential for a "legacy" VM. I think there are two main

1. Reduce your dependencies to things that you expect to be around in
10 years time.

2. Keep the data format stable.

For 1. it would be nice to use only standard C (POSIX ???), but due to
the way Qemu works, it needs to know about the link format used on
your platform. ELF seems to be a reasonable stable format, but we have
seen several transitions on Linux (glibc4, 5 and now 6), so there
could be more (incompatible) changes in the future.

2. is a question of development priorities. Assuming that Qemu 0.8
might not compile in 10 years time any more, Qemu 4.9 (or whatever we
have then) should be able to read Qemu 0.8 images. Maybe this is what
you mean by "improve disk image format". But since Qemu does supports
plain images, I do not see how you could make the format more stable

> So you see: in a commercial  and or industrial application one would like to 
> run
> the qemus on a server. At least the MS remote desktop protocol should work
> well. A qemu specific client would be nicer.

Actually X11 should work nicely, and it is much more open than RDP.
VNC also seems to be stable, but it is a lot less used.

> Unfortunately implementing the things that I was talking about would blow
> up the size of the code base dramatically. Qemu would never again be
> small, pretty and easy to understand. Where do you want to go?

I am not a developer, but I would prefer it small and pretty :-). If
it is not fast enough, wait 6 month and buy a faster CPU... But that
is just my personal view.


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