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Date:      Tue, 9 Jul 2002 12:59:25 +0400
From:      "Artem Tepponen" <temik@egartech.com>
To:        "Terry Lambert" <tlambert2@mindspring.com>, "Garrett Wollman" <wollman@lcs.mit.edu>
Cc:        "Mark Valentine" <mark@thuvia.demon.co.uk>, <arch@freebsd.org>
Subject:   RE: Package system flaws?
Message-ID:  <5235EF9BAE6B7F4CB3735789EEF73B29074172@turtle.egar.egartech.com>

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> From: Terry Lambert [mailto:tlambert2@mindspring.com]
> Sent: Tuesday, July 09, 2002 1:19 AM

> Specifically, another of the main problems, besides no "metadata
> first" priority, of the tgz format is that the index should be
> uncompressed while the contents are compressed. Historically, the
> whole archive, metadata and all, was compressed in order to support
> seperate uncompress and tar.  But it makes just as much sense to
> support seperate tar and uncompress -- i.e. compress the individual
> files, rather than compressing all files plus the metadata.  Most
> compression will work better on individual files rather than random
> file contents because of dictionary locality, anyway.

No, Terry. Dictionary locality works in a different way.
gzipped tar will almost always win vs. tarred gzipped files.
10-15% from memory. Just a quick check:

-rw-r--r--    1 temik    develops 29020160 Jul  9 12:36 gcc-3.0.1.gz.tar
-rw-r--r--    1 temik    develops 13821669 Jul  9 12:41 =
gcc-3.0.1.tar.bz2
-rw-r--r--    1 temik    develops 18054324 Sep 24  2001 gcc-3.0.1.tar.gz
-rw-r--r--    1 temik    develops 22746511 Jul  9 12:52 gcc-3.0.1.zip

Oops. I was wrong. >35% is a big difference. And bzip adds another 24%.
But for binaries difference between gzip vs. bzip2 will be smaller.

This is quite simple check but the picture will remain the same
for pretty any kind of data and hope that's enough to choose
single tar.somez + header.

Will header be combined or in a different file is another question.

Artem Tepponen


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