lzma compression on official isos vs Deltaisos

[Mike McCarty]

Tim wrote:
> On Tue, 2010-03-09 at 20:35 -0800, Antonio Olivares wrote:
>> The rpms are xz compressed but the isos are not.  That is what I am
>> asking, or is it too much compression?  When is so much too much?
> 
> Generally speaking, trying to compress something that's already
> compressed doesn't gain you anything.  Often, things will get bigger
> (e.g. new archive headers will be added to the file), and you're just
> creating more decompressing work to be done.

Yes, that's correct. However, when a file has very little
actual redundancy, sometimes recompression can have a dramatic
effect. In this case, it is unlikely that attempting compression
would help.

It is provable that any lossless compression algorithm which actually
causes one file to shrink must cause some other file to grow.

> The same applies whether trying to recompress the same file twice,
> directly.  Or, trying to compress something else containing them (the
> ISO with compressed files).

Mike
-- 
p="p=%c%s%c;main(){printf(p,34,p,34);}";main(){printf(p,34,p,34);}
Oppose globalization and One World Governments like the UN.
This message made from 100% recycled bits.
You have found the bank of Larn.
I speak only for myself, and I am unanimous in that!