> Could you do some tests, so we have more than conjecture to go on? > > What programs actually *benefit* from sparseness?
My primary motivation to do this is that I use P2P sharing program called BitTorrent. This program is written in Python and I run it in Cygwin. This program first creates whole file that I want to download by writing very few bytes with long distances between them and then fills it as it downloads chunks of the file from various other peers. The creation of this file takes from tens of seconds to few minutes without this patch, depending on size of the file. But with this patch it takes about two seconds to create this almost empty file. The files I usually download are movies. I don't experience any extra slowness while playing such created files. Vaclav Haisman
