Spin Down Hard Disk Programmatically on Windows?

Question

How do you request Windows to spin down a hard disk programmatically? Is there any user-mode function I can call (or kernel-mode function to call or IRP to send) in order to mak

Answer 1

I do not have an answer to the specific question that Mehrdad asked.

However, to help others who find this page when trying to figure out how to get their disk to standby when it should but doesn't:

1. I found that on a USB disk, MS PwrTest claims that the disk is off, but actually it is still spinning. This occurs even with really short global disk timeouts in win 7. (This implies that even if the system thinks it has turned the disk off, it might not actually be off. Consequently, Mehrdad's original goal might not work even if the correct way to do it is found. This may relate to how various USB disk controllers implement power state.)

2. I also found that the program HDDScan successfully can turn off the disk, and can successfully set a timeout value that the disk honors. Also, the disk spins up when it is accessed by the OS, a good thing if you need to use it, but not so good if you are worrying about it spinning up all the time to flush 1kB buffers. (I chose to set the idle timeout in HDDScan to 1 minute more than the system power manager timeout. This hopefully assures that the system will not think the disk is spun up when it is not.)

I note that powercfg has an option to prevent the idle clock from restarting from small infrequent disk writes. (Called "burst ignore time.")

You can get HDDScan here: HDDScan.com and PwrTest here: Windows Driver Kit. Unfortunately, the PwrTest thing forces you to have a lot of other MS stuff installed first, but it is all free if you can figure out how to download it from their confusing web pages.