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From:	"Markus Mauhart" <markus DOT mauhart AT chello DOT at>
To:	cygwin AT cygwin DOT com
Date:	Thu, 13 Mar 2003 16:09:54 +0100
MIME-Version:	1.0
Subject:	cygwin-1.3.21-1, problem with sparse file creation as default
Message-ID:	<3E70AD52.744.D4BC055@localhost>

I have a problem with the following new feature of cygwin-1.3.21-1

> - Create sparse files by default, when possible.  (Vaclav Haisman)

Couldnt it be made configurable, or removed ?


1) good old file manager (winfile.exe from NT4 system) does not display
sparse files - so all newly created files (through gcc, or make,
or "cp con 123.txt") are now invisible. (beside browsing, I didnt test real
file operations like move/copy a folder containing some sparse files)


2) AFAICS its advantages are very sparse ;-) Only when extending
a file's size the sytem (ntfs5+) automatically adds 'sparse' clusters.
Otherwise (even when writing 10G of all zero) not a single sector
is spared. Only programs aware of win32-sparse files profit from this
existing file-attribute when explicitely marking a range as zero,
but IMHO this is a micro-profit: such program can replace the following
code ....

  if (make_file_sparse(..)) mark_some_range_as_zero(..);

  ... with ...

  if (is_file_sparse(..)) mark_some_range_as_zero(..);

Note, this was assuming the win32 file API. Are there any cygwin/GNU
file API's (except for file creation;-) which when used then automatically
profit from sparse files ?


3) OTOH my guess is that it introduces more or less unnecessary resource
consumption (CPU and/or disk) ... one benchmark could be building
gcc and messuring time and disk consumption, but last time I built gcc
was in 2001; maybe Vaclav Haisman could benchmark the pros and cons
of this new feature. (also defragmenting a volume with 10.000 of such
newly created 'pseudo-sparse' files might pay a price)


Anyway, thanks for your attention,
Markus.


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