Changing dpkg-deb default compression from gzip to lzma for Hardy

Morten Kjeldgaard mok at bioxray.au.dk
Wed Dec 19 20:21:59 UTC 2007


Let me add my 2 cents' worth. I don't know what algorithm is used by  
lzma, but I think there are other factors than CPU speed and size  
that matters. Namely memory.

As an example, I can tell you that in the past we have experienced  
problems with the quite serious memory requirements of bunzip2. In  
several instances, we have seen bunzip2 fail for apparently  
mysterious reasons. Eventually, it turned out, the only way to solve  
the problem was to change the memory sticks on the motherboard. Even  
though memtest86+ did not reveal any problems with the RAM, bunzip2  
seems to be extremely sensitive to (I think) how well the particular  
type of memory is supported by the motherboard. It is possibly some  
kind of timing issue.

I want to emphasize that we never had problems running gunzip  
decompression even on the systems affected by the bunzip2 issue. As I  
said, I don't know the lzma algorithm at all, but I fear that in such  
an efficient compression procedure, there is a risk that similar  
problems could appear. Needless to say, failure to decompress  
packages properly could completely brick the system.

The gzip algorithm may not be the most efficient of all, but it is  
extremely reliable, fast, and memory-efficient.

IMHO, the 10% gain on the size of an install CD is quickly eaten by  
new/expanded packages, and soon, the same problem/discussion will  
return. I think the effort is better spent in making bone-hard  
priorities on what goes on the CD and what remains available from the  
archives.

And, perhaps, a special "try-me-out" CD edition could be designed,  
with samples of some of the latest and greatest software, but without  
some of the server tools and other stuff one would normally select  
for a running system.

Cheers,
Morten



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