Fwd: Re: cp command - problem with sparse

Corinna Vinschen corinna-cygwin@cygwin.com
Tue Feb 1 15:01:00 GMT 2005

On Feb  1 06:48, Eric Blake wrote:
> Hash: SHA1
> This question came up on the coreutils list:
> Does cygwin provide any support for sparse files on NTFS volumes that
> support it?  lseek() could be patched to use FSCTL_SET_ZERO_DATA when a
> seek jumps past the end of a file open for writing, but there is still the
> issue of when that file is given the FSCTL_SET_SPARSE attribute.

lseek already creates sparse files automatically in a write after lseek,
if the lseek seeked more than 128K beyond EOF.  128K is the value which
has been found to be the smallest sparse block size at which making
the file sparse makes a difference on XP.


Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          mailto:cygwin@cygwin.com
Red Hat, Inc.

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