Re: [Xen-users] Question about ioemu ...

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> > My HDA is configured like this:
> >
> > disk = [ 'phy:/dev/vms_1/win01,hda,w' ]
> >
> > My question , what is the diference if I configure like this ...
> >
> > disk = [ 'phy:/dev/vms_1/win01,ioemu:hda,w' ]
> >
> > What "ioemu" means ?
>
> It's simply a rudimentary attempt at ParaVirtual (PV) disk drivers on an
> HVM domain. Try it both ways, and 'cp' a *new* file to or from your dom0 
> and HVM domain, and time the difference. (I say new file, so you
> don'tmeasure the effects of caching.)

I don't think the "ioemu" argument actually does anything for block devices 
anymore.  As Jim suggested, it used to be used to specify whether a block 
device is an emulated (ioemu) or a paravirt disk.  Nowadays, I think HVM 
supports both paravirt and emulated modes for each disk so the switch isn't 
used.

PV drivers need to be enabled explicitly in the HVM guest, so you won't be 
able to measure a performance difference in IO unless you first install and 
configure these drivers.

Cheers,
Mark

-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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