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Message-ID:	<16072.6666.10124.338022@gargle.gargle.HOWL>
Date:	Sun, 18 May 2003 16:40:58 -0700
From:	Martin Buchholz <martin AT xemacs DOT org>
To:	"Max Bowsher" <maxb AT ukf DOT net>
Cc:	<cygwin AT cygwin DOT com>
Subject:	Re: SPARSE files considered harmful - please revert
In-Reply-To:	<003901c31d8c$6ec495f0$78d96f83@pomello>
References:	<16072 DOT 892 DOT 778395 DOT 24290 AT gargle DOT gargle DOT HOWL>
	<003901c31d8c$6ec495f0$78d96f83 AT pomello>
Reply-To:	martin AT xemacs DOT org

>>>>> "Max" == Max Bowsher <maxb AT ukf DOT net> writes:

Max> May I suggest a middle road? Why not let sparse files be configurable as a
Max> $CYGWIN option? This would allow those users who actually want them to
Max> enable them with minimal effort, but keep them off for most users.

I suspect that SPARSE files are genuinely useful, when storing large
files that have holes in them.  But I can't imagine one ever wanting
to use SPARSE for all files, because most files aren't like that.  So
I don't think sparseness is a good candidate for being put into
$CYGWIN.

We could have a much cleverer implementation of sparseness, if we kept
statistics on the number and size of zero bytes in a file while it was
being written.  When we did the close(), we could automatically
transform it into a sparse file.  But I don't think even that should
be the default behavior, because it would make all IO slower.

A program I might actually use myself is one that examines a file on
disk to see if it could be stored more compactly as a sparse file, and
transform it if that were the case.  Give it a -r option, and you
would have a "disk optimizer".  You can do something similar on Unix.

Martin

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