How to WriteFile to a PhysicalDrive (Windows 7) without getting ERROR_ACCESS_DENIED?

I'm trying to write a test pattern to every sector of a formatted USB drive. There is one logical drive (e.g. h:). This volume is FAT-formatted and contains data to be overwritten. Also, I want to overwrite the whole physical drive. The program is running with elevated user rights.

First I did the following:

// from the drive letter "h:" I get the physical disk number using
// IOCTL_VOLUME_GET_VOLUME_DISK_EXTENTS => "\\.\PhysicalDrive2"

hDevice = ::CreateFile( "\\.\PhysicalDrive2", GENERIC_READ|GENERIC_WRITE, 
  FILE_SHARE_READ|FILE_SHARE_WRITE, NULL, OPEN_EXISTING, 0, NULL ); 

// get the number of available sectors with IOCTL_DISK_GET_DRIVE_GEOMETRY_EX
// => ulNumberOfSectors

// now I try to write some sectors, e.g. 2 (I want to use a higher开发者_Python百科 value):
WriteFile( hDevice, abBuffer, 2*512, &byteswritten, NULL );

The call to WriteFile fails with ERROR_ACCESS_DENIED.

If I write one sector, it works.

When I overwrite the first sector and plug the device out and in again, Windows wants to format it. In this situation my code with 2048 sectors at once works without ERROR_ACCESS_DENIED.

I also unmounted the volume as described in CodeProject: WriteFile on Physical Drives with Windows 7 but this didn't change anything. Obviously the volume is unmounted because it's no longer visible in Windows Explorer.

I want to write more than a single sector due to perfomance reasons. I'm also afraid that other problems in the field might occur because I don't fully understand ths problem.

Any suggestions?

I didn't have problems with different WriteFile() sizes, but I did solve the

WriteFile(): Access is denied <ERROR_ACCESS_DENIED/5> to '\.\physicaldriveX

devices (usually USB HDD/SSD) in Windows 7 running as Administrator (elevated rights) as follows:

Computer Management -> Disk Management:

• Volume (H: in your case) -> right-click -> Delete Volume
• Disk (Disk 2 in your case) -> right-click -> Off-line
• Disk (Disk 2 in your case) -> right-click -> On-line

After that, I'm able to write to '\.\physicaldriveX' with no problem.

I think the Win7 locks (unlike previous Windows releases) the physical device as long as there is any file system on the device to avoid consistency problems.

You cannot directly access sectors of a drive which are owned by a mounted filesystem.

See Changes to the file system and to the storage stack to restrict direct disk access and direct volume access

The documentation for FSCTL_DISMOUNT_VOLUME describes the following sequence for overwriting a filesystem:

1. Open a volume.
2. Lock the volume.
3. Format the volume.
4. Dismount the volume.
5. Unlock the volume.
6. Close the volume handle.

Your pattern-writing operation would be in step 3 instead of formatting.

Another method is to use clean to delete all the partitions (and ALL DATA) on the disk:

C:\> diskpart
Diskpart> list disk

Diskpart> select disk N (where N is your disk number)

Diskpart> clean

Diskpart> exit