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Date: Mon, 19 May 2003 22:41:51 -0400
From: Christopher Faylor <cgf AT redhat DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: SPARSE files considered harmful - please revert
Message-ID: <20030520024151.GA1812@redhat.com>
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On Mon, May 19, 2003 at 07:27:06PM -0400, Bill C. Riemers wrote:
>> 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.
>
>It is rather obvious.  Let say you have three blocks worth of data, and
>is written into a file with a physical block followed by a sparse block
>followed by a physical block.  No disk space is reserved for the sparse
>block.  Why should it be, as it would defeat the whole purpose of using
>sparse files?  So physically on disk you have two consecutive physical
>blocks.  What then happens if you open the file in RW mode, seek to the
>sparse block and write some data?

1) You are assuming behavior that isn't documented.  I can imagine that
the first block could occupy, say 16 blocks and depending on the size of
the hole, there could be no fragmentation.

2) Normal read/write behavior would not result in a file that has a
sparse block.  I think it is a rare program which writes beyond EOF.  So
this would normally be a non-issue.

3) What no one seems to be mentioning is that we are trying to emulate
UNIX behavior here.  If the above is an issue for Windows then it could
also be an issue for UNIX.

cgf

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