drives that don’t respect Mac OS X’s power management settings?

[giorgos gen]

Here is what is stated by the author/developer of the software regarding the software...

"Makes sure that a selected drive does not go to sleep unexpectedly. For use with certain external drives that don’t respect Mac OS X’s power management settings."

Here is what i don't understand. How does MacOSX treat -as far as PowerManagement" settings are concerned- those certain ext.drives that don't respect OSX's power management settings? Does MacOSX have a power management setting that orders the drives to go to sleep but that setting is not respected by certain ext. drive enclosures? Is that what the software overrides, ext drives that put to sleep their installed drives?

[Jon Stovell]

In the Energy Saver preference pane in System Preferences, there is an option to "Put hard disks to sleep when possible." When this option is turned on, macOS will tell disks to stop spinning after a certain period of inactivity. 

• For internal disks this always works nicely; the internal disk will stay spinning as long as the computer is active. 
• For some external disks it also works nicely; these external disks don't do anything special to try to manage their activity and energy use, and so they just end up following the same instructions that macOS gives to the internal disks. 
• But other external disks include their own, independent power management in their firmware that more aggressively tries to go into a lower power state. The decision to spin down the disk is based not on whether the computer is active, but rather on how long it has been since this specific disk was last in active use. These disks don't care what macOS tells them.
  

If all you are using an external drive for is Time Machine backups or other things that happen in the background, aggressively spinning the disk down is probably the desired behaviour. But if you are using the disk to hold files that you use actively in a foreground process (e.g. your iTunes library), you normally want it to stay active the whole time the computer itself is active.

Since these external drives don't follow macOS's lead on whether to stay active or not, the only way to keep the drive awake is to make sure something happens to keep it in active use all the time. And so that's what this software does. It doesn't change any of the power management setting of your Mac or of your disk in any way at all. Instead, it just makes sure that once every 60 seconds, the content of a tiny file on the disk gets updated with new data. This ensures that the disk remains in active use the entire time that your computer is in active use.