Re: [Qemu-devel] QCow v2

["Christian MICHON" <christian.michon@gmail.com>]

ok, I did this experiment (long and painful).

a XP2003/SP1 qemu guest required 964,231,168 bytes qcow image.
zlib qcow image became 459,686,368 bytes.
lzma estimation (4k clusters) is 437,038,838 bytes.

Yes, 5% are still gained, but the time to get the lzma'ed qcow is
disastrous (especially on systems with anti-virus and anti-malware).

Do you still think it's worth it ?

On 7/4/06, Natalia Portillo <claunia@claunia.com> wrote:
> Just there is a question:
>
> If improvement is 5%, IS NOT THE SAME with a 5Mb HDD that with a 5Gb
> HDD.
>
> Wanna do testing with more real scenarios?
>
> Like a Windows XP full installation for example?
>
> I'm very sure that there will be a real difference.
>
> Regards
>
> El 04/07/2006, a las 15:51, Christian MICHON escribió:
>
> > for what it's worth:
> > qcow with "lzo -9" would become 4155352 bytes (bigger than original
> > zlib qcow).
> >
> > yet it's true at the compression and decompression stages that it
> > feels faster...
> >
> > On 7/4/06, Elefterios Stamatogiannakis <estama@dblab.ece.ntua.gr>
> > wrote:
> >> I agree
> >>
> >> Lzma and zlib are pretty much equivalent, so there is pretty much
> >> nothing to be gained except slightly more compression.
> >>
> >> On the other hand with lzo (1) there would be quite a considerable
> >> speed
> >> improvement at the cost of compression.
> >>
> >> It could also mean that reading on the qcow format could some
> >> times be
> >> faster (with compressible data) than   reading directly from the
> >> hard disk.
> >>
> >> lefteris
> >>
> >> (1) http://www.oberhumer.com/opensource/lzo/
> >>
> >> Johannes Schindelin wrote:
> >> > Hi,
> >> >
> >> > On Tue, 4 Jul 2006, Christian MICHON wrote:
> >> >
> >> >> how about also adding lzma compression for qcow ?
> >> >
> >> > Why lzma? We already have a dependency on zlib, why not just
> >> take that?
> >> >
> >> > Ciao,
> >> > Dscho
> >> >
> >> >
> >> > _______________________________________________
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> >>
> >>
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> >
> >
> > --
> > Christian
> >
> >
> > _______________________________________________
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> > http://lists.nongnu.org/mailman/listinfo/qemu-devel
> >
>
>
>
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-- 
Christian