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From: Rolf Campbell <rcampbell AT tropicnetworks DOT com>
Subject: Re: SPARSE files considered harmful - please revert
Date: Tue, 20 May 2003 11:01:08 -0400
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Christopher Faylor wrote:
> 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.
A agree that he is making an assumption, but he is probably right.  Even 
if 16 blocks are reserved for adding intermediate blocks, you would 
still end up with out-of-order blocks in the file; which isn't as bad as 
real fragmentation, but isn't as good as all blocks in order.

> 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
And it is.



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