[Linux-NTFS-Dev] Free Space calculation in NTFS

[Manoj S. <xm...@gm...>]

I don't seem to understand how free space is calculated in NTFS.

I have a 512MB Drive (NTFS)
Cluster size = 4k (512b per sector, 8 sectors per cluster)

$BITMAP file has 4 clusters (Last Cluster is 4032 bytes)
so the total bytes would be 3*4*1024 + 4032 = 16320

so the total clusters it can address 16320*8 = 130560
now 130560*4096 = 510MB (total usable disk space i am guessing)

now if i calculate the total bits that are 0 in $Bitmap that should
give me the total free space
But total 0 bits are only 424.. that means only 424 clusters are free i.e.1696KB

But the disk is 441MB full and 68.6MB free.

(i have really checked my free 0's code it looks ok)

Can anyone please explain this to me?