Re: SPARSE files considered harmful - please revert

[Rolf Campbell <rcampbell at tropicnetworks dot com>]

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.



--
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/