What does "Turn off Hard Disk after ... " actually do?

Hi,

This may seem to be a dumb question, but what does "Turn off Hard Disk after ... " in the advanced section of the powers setting actually do?

For example, if I have several background programs (say Virtualbox, defragmenter, and Acronis Backup) running and accessing the hard disks. Will this particular power setting still turn off my hard disks if they are accessed by background programs but the user hasn't touched the computer for, say, 20 minutes (with the power setting being "Turn off Hard Disk after 20 minutes")

Also, suppose I have three hard disks, only two of which are being accessed. So, will Windows turn that drive off, selectively, or will it keep turned on/power-down all the drives together?

Lastly, do the above conditions apply to external hard disks too?

Thanks in advance for help!

Hi dhruv17singhal-

...what does "Turn off Hard Disk after ... " in the advanced section of the powers setting actually do?

I believe it sets the time interval for inactivity of a hard disk before it will go into sleep mode and park itself.

In my experience, every time the hard disk needs to be accessed for a long period of time, say a virus check, system backup or defragmenting, I make sure to set the Power Options to High Performance. I have returned to my system having left it on Power Savings mode and awoken it from sleep to find the hard disk process (virus check etc.) resuming where it left off before sleeping. Besides that, I have also noticed that HD performance is usually better when not in Power Savings.
When sitting in front of the system and actively working, I usually use the Balanced setting.
It would be nice to have the option of selecting which drives sleep and which don't for those volumes rarely used-
JohnPC

I conclude that it would be best for me to keep the settings for "Best Performance."

Thanks JohnPC and rap33042 for the information you provided.