I recently wrote that LZMA has been used to pack more languages
onto the LiveCD. Here are some charts that show how LZMA
stacks up against someof the other popular compression algorithms.
(apologies for the poor image quality, open in another window 
for a clearer image)



These tests were run on a LiveCD archive using 7za(1). 
As you'll note, the compression ratio provided by LZMA is
about 35% better than gzip-9. However, LZMA is more
CPU intensive and as a result the compression and
decompression speed is slower than the alternatives.

So, for some use cases the cpu versus compression
tradeoff might make LZMA unsuitable but for the LiveCD
use case, it is reasonable provided we architect our
solution such that the decompression speed isn't a bottleneck
(Compression speed isn't a problem for the LiveCD architecture)

The OpenSolaris 2008.05 release that is going to come
out sometime in May is going to have two versions of
the same LiveCD, one with a limited set of languages and
locales and another one with a more fuller set of languages.

One of the big challenges with creating a LiveCD with a
full set of languages was that there was limited amount
of available free space on the CD to allow for including
all the languages. How do you cram more stuff on the CD?
Compress it harder, I say! Even better, compress it with
LZMA!

The OpenSolaris kernel did not have an in-kernel implementation
of LZMA that could be taken advantage of (why do we need an
in-kernel implementation, I'll answer that in a separate blog entry). 
So, in our quest to provide one, we started looking at the LZMA SDK. 
Some of the challenges with porting the source from this SDK to the  
OpenSolaris kernel were that our lawyers were not amenable to the licensing 
terms and the compression code was all written in C++ (which, 
for the uninitiated, is strongly desisted in the kernel).

If you've ever dealt with lawyers you'll be quick to spot
that the licensing can be particularly troublesome. It was. 
But only until we contacted with author of LZMA, Igor Pavlov.
Igor was not only willing to relicense the source code under
CDDL (which would ofcourse be agreeable to the lawyers) but
also willing to re-write the compression code in C. And, he 
did that in just a matter of couple of weeks -  truly outstanding. 
That, to me, is the power behind open source and the sharing 
opportunities it provides for the broader good.

So, thank you Igor for an excellent compression algorithm
in LZMA and thanks for all your assistance in making the
OpenSolaris 2008.05 release what it is. We look forward to
working with you in the future too.