RPM compression format

[Jindrich Novy]

On Thu, Jun 19, 2008 at 01:51:50PM -0400, Michael Wiktowy wrote:
> Hi,
> 
> I just read http://www.linuxformat.co.uk/static/suse11.html where is
> mentions that OpenSuSe 11 went with a different compression algorithm
> for their rpms (LZMA instead of bz2) and have a few questions:
> 
> 1) While every distro seems to be coming together on a package
> management GUI (PackageKit), does this represent a splintering of
> package formats? or is rpm compression algorithm agnostic? Is there
> any hope that the various rpm development will start pulling in the
> same direction?

Yes. We already have the LZMA bits in the upstream RPM for a while. So
the support for the LZMA payload compression will occur as soon as the
head RPM lands in rawhide. Support for old gz/bz2 payload remains, so
no regressions will be introduced.
> 
> 2) LZMA appears to have some good characteristics for installation
> rpms (tighter compression, 50% decompression time ... at least as
> implemented by 7zip ref:
> http://www.maximumcompression.com/data/summary_mf4.php ). Is Fedora
> planing to follow this switch (or has it already and not advertised it
> as a prominent feature) or are there other considerations preventing
> that (patent issues?, not suitable for delta rpms?, 200% compression
> time)?

Agreed, LZMA shows amazing compression results better that bzip2 with
faster decompression than bz2 in most cases. OTOH it consumes more
memory and compression takes longer, but seems to be feasible with the
-7 compression level (default).

The exact timing for the new rpm release is not clear yet, but there
would be a need of mass rebuild to fully take advantage of the new
compression.

> /Mike
> 
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-- 
Jindrich Novy <jnovy at redhat.com>   http://people.redhat.com/jnovy/