Mailing-List: contact cygwin-help@cygwin.com; run by ezmlm List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner@cygwin.com Mail-Followup-To: cygwin@cygwin.com Delivered-To: mailing list cygwin@cygwin.com Date: Tue, 20 May 2003 13:14:46 -0400 From: Christopher Faylor To: cygwin@cygwin.com Subject: Re: SPARSE files considered harmful - please revert Message-ID: <20030520171446.GC14348@redhat.com> Reply-To: cygwin@cygwin.com Mail-Followup-To: cygwin@cygwin.com References: <16072.6666.10124.338022@gargle.gargle.HOWL> <00f301c31e12$c29efdb0$6400a8c0@FoxtrotTech0001> <00be01c31e15$944d0d50$78d96f83@pomello> <005601c31e26$77671260$6400a8c0@FoxtrotTech0001> <20030519175913.GA24066@redhat.com> <008001c31e5e$39c0c680$6400a8c0@FoxtrotTech0001> <20030520024151.GA1812@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.1i On Tue, May 20, 2003 at 11:01:08AM -0400, Rolf Campbell wrote: >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. No, you wouldn't. If you allocate a block, skip 4 blocks, write a block, go back to the begining, skip a block and write a new block, I would not be surprised to see that there is no fragmentation. You would end up with a potential gap in the middle of the file but that isn't necessarily even a bad thing given rotational latency. It's not as simple as saying "there's a gap so it must be bad". As usual, however, this discussion is really not worth the effort that goes into it given the number of sparse files out there. >>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. > >And it is. So there goes your argument. You can't argue that you want cygwin to behave differently from unix and really win. cgf -- Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple Problem reports: http://cygwin.com/problems.html Documentation: http://cygwin.com/docs.html FAQ: http://cygwin.com/faq/