After multiple recent support issues with SanDisk brand USBs, we don't recommend buying SanDisk USBs for Unraid at this point.    Either due to counterfeit devices being sold or a manufacturing change directly from SanDisk, multiple users have attempted to boot SanDisk USBs and found out that they do not register a unique GUID and therefore, cannot be properly licensed with Unraid. Multiple attempts at contacting SanDisk on this issue have gone nowhere.   For a great rundown