[Qemu-devel] image size - OS reports 720mb, but image file is 2.3 gig

[Qemu-devel] image size - OS reports 720mb, but image file is 2.3 gig

[Joe Bogner]

Hello,

I'm trying to create an win2k image that is as small as possible. I'd
like to be able to copy the image back and forth between machines so
that I have a complete win2k development image.

According to win2k, the size is about 720mb. Originally win2k was
reporting the size to be about 1.2gig, but I was able to reduce it
through NTFS compression.

Here's the dilemna. The physical image file is 2.3gig. I've run a
qemu-img convert -f qcow <input> -O qcow <output>, which took the
original 4.5 gig image down to 2.3 gig. With qemu-img compression, I
was able to get it down to 1.7gig.

Why is there such a large discrepency between what win2k reports and
the physical image file on disk? Is there anything else I can do to
reduce it, aside from compressing the physical image file?

1.7 gig is still quite a bit to be shuffling around between machines.

Thanks,
Joe

Re: [Qemu-devel] image size - OS reports 720mb, but image file is 2.3 gig

[Mike Kronenberg]

Have you tried to defrag your Partition? If you only have one block of 
data and one block of free space, compression will be much more effective.

G V

Re: [Qemu-devel] image size - OS reports 720mb, but image file is 2.3 gig

[Joe Bogner]

Yes. That was one of my first steps. Thanks for the response.


On Fri, 11 Feb 2005 15:27:40 +0100, Mike Kronenberg
<mike.kronenberg@kberg.ch> wrote:
> Have you tried to defrag your Partition? If you only have one block of
> data and one block of free space, compression will be much more effective.
> 
> G V
>

Re: [Qemu-devel] image size - OS reports 720mb, but image file is 2.3 gig

[Paul Brook]

On Friday 11 February 2005 14:18, Joe Bogner wrote:
> Hello,
>
> I'm trying to create an win2k image that is as small as possible. I'd
> like to be able to copy the image back and forth between machines so
> that I have a complete win2k development image.
>
> According to win2k, the size is about 720mb. Originally win2k was
> reporting the size to be about 1.2gig, but I was able to reduce it
> through NTFS compression.
>
> Here's the dilemna. The physical image file is 2.3gig. I've run a
> qemu-img convert -f qcow <input> -O qcow <output>, which took the
> original 4.5 gig image down to 2.3 gig. With qemu-img compression, I
> was able to get it down to 1.7gig.
>
> Why is there such a large discrepency between what win2k reports and
> the physical image file on disk? Is there anything else I can do to
> reduce it, aside from compressing the physical image file?
>
> 1.7 gig is still quite a bit to be shuffling around between machines.

Even if files have been deleted/compressed the data will still be there on the 
disk. qemu can't tell the difference between "useful" data, and unused data 
that can be discarded. You need to make sure all the unused space on the 
image is actually zeroed.

One way to achieve this would be to shrink the guest partition to its minimum 
size, then create a second partition on the unused space and explicitly zero 
that out (using dd from knoppix if necessary).

Paul

Re: [Qemu-devel] image size - OS reports 720mb, but image file is 2.3 gig

[Joe Bogner]

WipeDisk did the trick on Windows. My physical disk image is now the
same size as what the guest OS reports.

WipeDisk - http://www.birdcomputer.ca/Software/SoftwareToC.html

Thanks for your help.


On Fri, 11 Feb 2005 15:03:04 +0000, Paul Brook <paul@codesourcery.com> wrote:
> On Friday 11 February 2005 14:18, Joe Bogner wrote:
> > Hello,
> >
> > I'm trying to create an win2k image that is as small as possible. I'd
> > like to be able to copy the image back and forth between machines so
> > that I have a complete win2k development image.
> >
> > According to win2k, the size is about 720mb. Originally win2k was
> > reporting the size to be about 1.2gig, but I was able to reduce it
> > through NTFS compression.
> >
> > Here's the dilemna. The physical image file is 2.3gig. I've run a
> > qemu-img convert -f qcow <input> -O qcow <output>, which took the
> > original 4.5 gig image down to 2.3 gig. With qemu-img compression, I
> > was able to get it down to 1.7gig.
> >
> > Why is there such a large discrepency between what win2k reports and
> > the physical image file on disk? Is there anything else I can do to
> > reduce it, aside from compressing the physical image file?
> >
> > 1.7 gig is still quite a bit to be shuffling around between machines.
> 
> Even if files have been deleted/compressed the data will still be there on the
> disk. qemu can't tell the difference between "useful" data, and unused data
> that can be discarded. You need to make sure all the unused space on the
> image is actually zeroed.
> 
> One way to achieve this would be to shrink the guest partition to its minimum
> size, then create a second partition on the unused space and explicitly zero
> that out (using dd from knoppix if necessary).
> 
> Paul
>

Re: [Qemu-devel] image size - OS reports 720mb, but image file is 2.3 gig

[Charles Longeau]

Hello,

> You need to make sure all the unused space on the
> image is actually zeroed.
> 
> One way to achieve this would be to shrink the guest partition to its minimum
> size, then create a second partition on the unused space and explicitly zero
> that out (using dd from knoppix if necessary).

I think there is a easier way to zero unused space on an image or partition.

Mount the image/partition
cd into it
cat /dev/zero > dummy_file
(Wait until error : No space left on device)
rm dummy_file

Hope it helps,

Best regards,

Charles Longeau

Re: [Qemu-devel] image size - OS reports 720mb, but image file is 2.3 gig

[Elefterios Stamatogiannakis]

  I have done exactly that:
-Win2k SP4
-Office 2000
-Adobe Pro 6
-Mozilla suite
-Some other stuff.

  Contained in a cd compressed with Drive Image.
  Uncompressed it is 1.2 GB.
  It is certainly doable.

  Furthermore it works at whatever machine you put it in provided that 
you have the drivers for it EXCEPT pcs with sata.

  I could (privately) provide the image if you want to take a look at it 
but i don't want redistribution.

  Under qemu some things don't work (i have posted an account of that in 
the qemu list previously). I think that the root of all qemu problems 
under windows has something to do with the date/time of the emulated 
machine.

  lefteris.

Joe Bogner wrote:
> Hello,
> 
> I'm trying to create an win2k image that is as small as possible. I'd
> like to be able to copy the image back and forth between machines so
> that I have a complete win2k development image.
> 
> According to win2k, the size is about 720mb. Originally win2k was
> reporting the size to be about 1.2gig, but I was able to reduce it
> through NTFS compression.
> 
> Here's the dilemna. The physical image file is 2.3gig. I've run a
> qemu-img convert -f qcow <input> -O qcow <output>, which took the
> original 4.5 gig image down to 2.3 gig. With qemu-img compression, I
> was able to get it down to 1.7gig.
> 
> Why is there such a large discrepency between what win2k reports and
> the physical image file on disk? Is there anything else I can do to
> reduce it, aside from compressing the physical image file?
> 
> 1.7 gig is still quite a bit to be shuffling around between machines.
> 
> Thanks,
> Joe
> 
> 
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