mistaken about that. It might have been related to the appearance of
high-water marking if that wasn't present in the earliest versions

NTFS was always supporting ValidDataLength _on disk_.

All Windows's FSDs support this _in memory (as an FCB field)_, but on-disk support is NTFS-only.

Sorry to forget this seek+SetEndOfFile sequence. I was only thinking about ZwCreateFile with AllocationSize.

--
Maxim S. Shatskih
Windows DDK MVP

http://www.storagecraft.com