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Date: Mon, 19 May 2003 13:59:13 -0400
From: Christopher Faylor <cgf-rcm AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: SPARSE files considered harmful - please revert
Message-ID: <20030519175913.GA24066@redhat.com>
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On Mon, May 19, 2003 at 12:46:19PM -0400, Bill C. Riemers wrote:
>
>> Um? By my understanding, making a file sparse can never be dangerous. It
>can
>> cause sub-optimal performance, but code reading the file doesn't have to
>be
>> aware of anything special - the OS takes care of it.
>
>I remember there use to be a warning the man page that file system holes can
>cause seek offsets to be wrong for programs that do seek's across or into
>hole boundries.  The original Linux code only handled when code was loaded
>as a result of an mmap which happens for exec's and dlopen.  It could be by
>now these restrictions have been eliminated.  I notice the latest GNU cp
>info page lists sparse files a filesystem capacity not a kernel capability,
>and the logic for --sparse=auto simply copies a file as-is, nothing smart
>like checking for the execution bit.
>
>I looked through the NTFS document on MSDN.  It seems at least for NTFS
>there is no restriction on what types of files can be sparse.  Of course, if
>you make files sparse that are going to be accessed with RW operations, you
>are going to fragment the file.

I think you need to read the documentation a little more closely.  Either that
or provide references to the parts of the documentation that says that normal
RW operations would fragment a sparse file.

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