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Date: Mon, 19 May 2003 16:08:49 -0400
From: "Pierre A. Humblet" <pierre DOT humblet AT ieee DOT org>
To: cygwin AT cygwin DOT com
Subject: Re: SPARSE files considered harmful - please revert
Message-ID: <20030519200848.GA246379@Worldnet>
References: <Law10-F79o4cWScPAA600033a95 AT hotmail DOT com> <028f01c31e38$0e428c30$78d96f83 AT pomello>
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On Mon, May 19, 2003 at 07:54:19PM +0100, Max Bowsher wrote:
> John Vincent wrote:
> >
> > I looked up sparse files on MSDN and found the following link:
> >
> >
> http://msdn.microsoft.com/library/default.asp?url=/library/en-us/fileio/base/sparse_file_operations.asp
> >
> > The most interesting thing is that a sparse file is only sparse if the
> zeros
> > in the file are written with a special operation. I strongly suspect that
> > the patch to support sparse files introduced in cygwin is incorrect (or at
> > least incomplete)
> 
> Areas that are simply seeked over, and never written to, should be sparse as
> well.

Not only they "should be", they are.
 
> Anyway:
> 
> Based on the posted numbers, global use of sparse files is a bad idea. Can
> we conditionalize sparse files on a $CYGWIN option? (Or something else, I
> don't mind, but the important thing is that it should not be on by default.)

Why not make in on by default *when it can help*, i.e. when the write() leaves
holes? 

Pierre


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