Subject: Re: SPARSE files considered harmful - please revert
From: Martin Buchholz <[email-masked]>
To: "Max Bowsher" <[email-masked]>
Cc: <[email-masked]>
Date: Sun, 18 May 2003 16:40:58 -0700

>>>>> "Max" == Max Bowsher <[email-masked]> 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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