So I'm not a Windows expert but I've done file system work. If windows is reasonably smart it will support files with unallocated blocks. Setting the length t

So I'm not a Windows expert but I've done file system work. If windows is reasonably smart it will support files with unallocated blocks. Setting the length to 8GB is not the same as writing 8GB in any reasonable file system. I'd retry with a script that actually writes the data.