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Date: Fri, 14 Mar 2003 00:51:06 +0100
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: cygwin-1.3.21-1, problem with sparse file creation as default
Message-ID: <20030313235106.GA16264@cygbert.vinschen.de>
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On Fri, Mar 14, 2003 at 12:32:55AM +0100, Markus Mauhart wrote:
> > On Thu, Mar 13, 2003 at 04:09:54PM +0100, Markus Mauhart wrote:
> Never had a problem. Do you really think that NT4sp4 broke it (without
> eventually fixing it in sp5,6) ? Works w/o problems on w2k; didnt work
> with XPbeta/RC, but this has been fixed for XP's release ( -> probably
> some VIPs at MS use winfile.exe ;-)

Don't know the details, sorry.

> > I've checked it, it's no problem to view the files in explorer under NT4. 
> 
> You mean w2k or wXp (or does NT4spx support ntfs5 including read/write
> sparse files) ? Anyway, explorer on XP has no problem with the new
> cygwin's sparse files.

No I meant NT4.  Think 'network share'.  You began this thread mentioning
NT4, right?

> > Nope.  All applications using seek instead of blindly writing zeros
> > to the file do profit.  And also this is default on modern UNIX boxes.
> 
> Now i'm confused: with "seek", did you mean the case I called "extending
> a file's size" ? IMHO less than 0,01% of such file expansions really end

Yes, seeking beyond the current EOF.  Where did you get the number 0.01%?
Just guessing I guess.

> "this is default on modern UNIX boxes" ... what ? And is it a property
> of the filesystem-data, FS-driver or an OS feature ?

Files are "just sparse".  It's a FS driver property.

> Another reason that makes me suspicious: ntfs5 with sparse files is
> released since 3/2000, but nevertheless neither w2k nor wxp nor any of
> the servers AFAIK provide even the option of creating all new files
> in a directory or volume as sparse files - have the guys at MS missed
> the performance benefits that cygwin-1.3.21-1 now claims, or do they
> know it (their NTFS5x !) better ?

We don't claim performance benefits.  AFAIK, sql server is using sparse
files.  I have no idea why MS doesn't make this be default, perhaps just
because they are careful with backward compatibility, who knows?

> But note, after reading your remarks concerning the previous discussions
> in the patches list I've found it and will go through it, maybe this
> thread has enough new & good arguments to convince me and make me smarter.

Personally I found no good arguments in that thread.  The only people
who actually tested that feature were Vaclav (the contributor of the
patch) and me.  I had no negative experience from my tests and, especially
positive, mmap() still works, so I have no reason to change anything.
Anybody who wants a change has to come up with a testcase showing what's
supposedly bad with the patch.

Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Developer                                mailto:cygwin AT cygwin DOT com
Red Hat, Inc.

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