in reply to Need Advice on Folder/Drive locking

Not sure if windows supports sparse files but I did the same task in unix by making a *SPARSE* lock file that was the same size as the file I was copying and used that in my size calculations. 

        sysopen( $fh, $lock_filename, O_RDWR | O_CREAT );
        seek($fh, $filesize,0);
        truncate($fh,$filesize);

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Then a stat call gives us the sparse size while the filesystem hasn't grown at all. To get a rough idea of free space you can tally the free space the FS reports minus the sum of the size of all your sparse lock files.

Update: Code typos fixed

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Re^2: Need Advice on Folder/Drive locking
by Marshall (Canon) on Feb 05, 2010 at 08:49 UTC
    interesting idea. Yes, Windows NTFS does support sparse files. to make one...see below.

    One link http://msdn.microsoft.com/en-us/library/aa365564(VS.85).aspx
    Google "windows sparse file" for others including "FSUTIL Sparse" command line manager on Win XP. 

    #!/usr/bin/perl -w
use strict;

open(FILE, ">", "sparse") || die "unable to open for write\n";

print FILE "some stuff";
seek(FILE,1000000,0);
print FILE "more stuff";
close FILE;

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