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Date:      Fri, 17 Mar 2000 15:41:00 -0500
From:      John LoVerso <loverso@infolibria.com>
To:        Tom Embt <tom@embt.com>, freebsd-current@FreeBSD.ORG
Subject:   Re: Why not gzip iso images?
Message-ID:  <38D2985C.F090D9C9@infolibria.com>
References:  <8aorf2$htp$1@atlantis.rz.tu-clausthal.de> <3.0.3.32.20000317092038.0078a018@mail.embt.com>

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> Had
> the file been split and a checksum computed for each piece, I could have
> grabbed only the affected portion of the ISO.

This is screaming for an FTP server mod similar to the wuftpd code that will
automatically run tar|gzip.  That is, given a file "foo", serve "foo.aa" to be
the first (server-defined) chunk size of the file.  Define "foo.md5" to be a
(precomputed) list of md5 checksums for each chunk.  The ftp server
automatically just open's and seeks in the single file and returns the proper
amount of bytes.

Result: server only stores 1 copy (the whole, large file), the clients can grab
either the whole or the parts.

For instance,
ftp://ftp.freebsd.org/pub/FreeBSD/releases/4.0-RELEASE/bin/bin.tgz  might be
served with a chunk size of 235Kb.


BTW, other than the checksums, it is possible for an ftp client to grab
arbitrarily sized chunks of a file using the FTP "RESTart" option.  I don't know
of a client that supports this, but it would be easy to add.

John


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