a1nt

Thank you very much! It works!

I have the same problem with uTorrent. And I have some suggestion why this happens. In the uTorrent settings, write caching is disabled by default. I think this causes the files to be opened with the flag FILE_FLAG_NO_BUFFERING. The data to write must be aligned by the size of the physical sector. For a DrivePool volume, the sector size is always 512 bytes. On most disks, this does not lead to problems, because their sector is also 512 bytes. But on the 4Kn (Advanced Format 4K Native) drives, the error "Incorrect function" occurs because it requires alignment to 4096 bytes. I tried to call the GetDiskFreeSpace function, and here are the results: 1. WD Red: BytesPerSector = 512 2. HGST HC510 (4Kn): BytesPerSector = 4096 3. DrivePool volume: BytesPerSector = 512 (My disk pool contains several WD Red and one HGST HC510.) I also tried to download the file in different ways: 1. Directly on WD Red: OK. 2. On WD Red in the pool: OK. 3. Directly on HGST: OK. 4. On the HGST in the pool: error "Incorrect function". I think that it is possible to fix the problem by making GetDiskFreeSpace (and disk geometry queries via IOCTL) to return the maximum sector size of all pool disks. Can you fix it? Thanks!