emergency file server cleanup

Alexandre Oliva lxoliva at fsfla.org
Mon Oct 6 02:44:26 UTC 2014

On Sep 29, 2014, Antonio Diaz Diaz <antonio at gnu.org> wrote:

> Alexandre Oliva wrote:
>>> Why? Lzip can compress more than xz with a bit of tuning via --options.
>> Maybe it can, but when I compared the sizes of the files to decide which
>> one to keep, .xz files were consistently (if slightly) smaller than .lz
>> ones.

> I guess you mainly mean tarballs

I meant total disk space used by all .xz files, compared with all .lz
files.  It is true that tarballs, being much bigger than the other
files, dominated the difference, which ended up favoring xz.

> Vcdiff is already a compressed format. I guess the best option is not
> to compress it again and just distribute one plain .vcdiff file per
> release. You save about 66% in size and the (re)compressing time.

Yeah.  I'm not even sure I should keep on using vcdiff.  It doesn't seem
to be a useful format for the case at hand.  The xdelta 1 format was far

> In the lzip benchmark you can also see that each and every one of the
> 43 xz tarballs being distributed in ftp.gnu.org were better compressed
> by lzip.

AFAICT, deblob-main passes -9 to bzip2, xz and lzip.  I don't mean to be
doing anything disfavorable to lzip; quite the opposite.  Am I?  Isn't
setting lzip's -9 to lower limits than xz sort of self-defeating?

> Lziprecover is so awesome that people can't believe it. :-) Most think
> it is just like bzip2recover.

I'm not familiar with bzip2recover either ;-)

> Lziprecover can repair perfectly most files with a single-byte error
> on them, without the need of any extra redundance at all. The repaired
> file will be identical bit for bit to the original.


> One byte may seem small, but most file corruptions not produced by I/O
> errors just affect one byte, or even one bit, of the file.

This matches my experience.  I wish I could have used lziprecover on
archives that got corrupted due to faulty memory chips at some point.
Unfortunately, they weren't lzip archives to begin with, and even if
they were, I didn't know about lziprecover back then ;-)

> Be the change you wish to see in the world. Drop xz tarballs altogether. ;-)

That's sort of tempting, since xz takes the longest to compress among
the 3 compression formats I use, but I'm not sure I'm ready to undertake
such a bold step ;-)

Alexandre Oliva, freedom fighter    http://FSFLA.org/~lxoliva/
You must be the change you wish to see in the world. -- Gandhi
Be Free! -- http://FSFLA.org/   FSF Latin America board member
Free Software Evangelist|Red Hat Brasil GNU Toolchain Engineer

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