LaCie HD wakes up even iMac is sleeping

Hello!

Since some weeks I have a LaCie HD for backup with TimeMachine. The strange thing is that even when the iMac is asleep the HD starts up for a short moment (about once an hour I guess). I have installed TimeMachine Scheduler and scheduled no backups during the night.
Still the HD starts up. Aperently there is a process checking once and a while if the HD is still present and this wakes the HD up. Which process is this?

My question is how can I avoid this?

Thanks for any help.

Shut the iMac down, rather than put it to sleep.

Yes thats clear but not the idea. Any suggestions which process might trigger the HD?

It depends. Mac OS runs routine maintenance (though I'm not sure if it does in sleep mode), and maybe if you have files stored on the external (like MP3 in iTunes as an example) it will spin up the drive to access it. Either that or it could just be testing the connected USB devices.

Exactly as you describe but which processes are active and how can I avoid them starting to check? That's my question.

I don't think you can, it's considered essential by the OS. All you can do is eject the drive when you put the Mac to sleep.

It's probably just indexing, you could just set up your energy settings to put the iMac to sleep after a certain period of time (15 mins for me). That way it doesn't really matter.

G3XOI said:

It's probably just indexing, you could just set up your energy settings to put the iMac to sleep after a certain period of time (15 mins for me). That way it doesn't really matter.

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Sorry I do not understand you correctly. The energy settings are already set to put the iMac to sleep after 15 min. But once asleep automatically or manually by pressing alt mac arrow the HD starts up. It could be indexing but were do I exclude the HD from being indexed?

Found How to disable spotlight index for specific folder in Mac OS X? - Techie Corner excluding HD from being indexed by spotlight. Maybe this helps.