Question

How do I enable “Better Performance” on an External USB HD programatically in C/C++.

Specifically I am talking about the device properties pane in the control panel in Microsoft Windows. That enables a form of OS level write caching.

Answer 1

This link Provided by Alex K. is my accepted answer: It deals with the IOCTL_DISK_SET_CACHE_INFORMATION DeviceIoControl()

http://blogs.msdn.com/b/dhawan/archive/2009/10/05/enable-or-disable-enable-write-caching-on-disk-behavior-on-disk.aspx

#define _WIN32_WINNT 0x0503

#include <windows.h>

DISK_CACHE_INFORMATION info;
DISK_CACHE_INFORMATION rinfo;


void main(void)
{
    DWORD rr;
    HANDLE hDevice;
    DWORD err;
    DWORD returned;

    hDevice = CreateFile("\\\\.\\C:", // drive to open
                GENERIC_READ | GENERIC_WRITE,
                FILE_SHARE_WRITE | FILE_SHARE_READ, 
                // share mode
                NULL, // default security attributes
                OPEN_EXISTING, // disposition
                FILE_ATTRIBUTE_SYSTEM, // file attributes
                NULL); // do not copy file attributes
    if(hDevice==INVALID_HANDLE_VALUE)
    {
        return;
    }

    rr = DeviceIoControl(hDevice,IOCTL_DISK_GET_CACHE_INFORMATION,NULL,
                        0,(LPVOID)&info,(DWORD)sizeof(info),(LPDWORD)&returned,    (LPOVERLAPPED)NULL);
    if (!rr)
    {
        err = GetLastError();
        return;
    }

    info.WriteCacheEnabled = true;
    info.ReadCacheEnabled = false;
    info.DisablePrefetchTransferLength = 1;

    rr = DeviceIoControl(hDevice,IOCTL_DISK_SET_CACHE_INFORMATION,(LPVOID)&info,(DWORD)sizeof(info),
                        NULL,0,(LPDWORD)&returned,(LPOVERLAPPED)NULL);
    if (!rr)
    {
        err = GetLastError();
        return;
    }

    rr = DeviceIoControl(hDevice,IOCTL_DISK_GET_CACHE_INFORMATION,NULL,0,
                        (LPVOID)&rinfo,(DWORD)sizeof(rinfo),(LPDWORD)&returned,(LPOVERLAPPED)NULL);
    if (!rr)
    {
        err = GetLastError();
        return;
    }

    CloseHandle(hDevice);
}

---

Old Information:
Windows 2K did contain a “Power Protected” Write Cache Option, but it was never carried over to Windows XP. Which makes a comment about using Dskcache.exe invalid. Was “Power Protected Mode” ever put back into e.g. Windows Vista? I do not know.