Create new files as sparse on NT systems. (2nd try)

Max Bowsher
Wed Feb 19 00:27:00 GMT 2003

Vaclav Haisman wrote:
> On Tue, 18 Feb 2003, Gary R Van Sickle wrote:
>> "Note: It is up to the application to maintain sparseness by writing
>> zeros with FSCTL_SET_ZERO_DATA", sez the Platform docs.
> In this respect Windows are ahead of any recent Unix system. I wasn't
> able find any Unix/Posix syscall that would allow this unlike Windows.
>> Even if you do WriteFile()s with all zeros on a sparse file, you are
>> actually hitting the disk.
> Have you ever tryed the same thing in Unix environment? Writing
> buffer full of zeros with write syscall won't gain you anything
> either. All the zeros will be physicaly written onto the disk. This
> means it has the same behaviour as Unix systems.
>> The only thing this patch will do AFAICS is set a bit somewhere in
>> the guts of NTFS that will be pretty much ignored.  I'm with Max, I
>> don't see the benefit and can only imagine the consequences.
> I don't see any negative consequences of this patch. The only one I
> can imagine it can slow down file operations but I very very doubt it.

Could you do some tests, so we have more than conjecture to go on?

What programs actually *benefit* from sparseness?


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